1 . “You can use me as a last resort(选择), and if nobody else volunteers, then I will do it.” This was an actual reply from a parent after I put out a request for volunteers for my kids’ lacrosse(长曲棍球) club.

I guess that there’s probably some demanding work schedule, or social anxiety around stepping up to help for an unknown sport. She may just need a little persuading. So I try again and tug at the heartstrings. I mention the single parent with four kids running the show and I talk about the dad coaching a team that his kids aren’t even on … At this point the unwilling parent speaks up, “Alright. Yes, I’ll do it.”

I’m secretly relieved because I know there’s real power in sharing volunteer responsibilities among many. The unwilling parent organizes the meal schedule, sends out emails, and collects money for end-of-season gifts. Somewhere along the way, the same parent ends up becoming an invaluable member of the team. The coach is able to focus on the kids while the other parents are relieved to be off the hook for another season. Handing out sliced oranges to bloodthirsty kids can be as exciting as watching your own kid score a goal.

Still, most of us volunteers breathe a sigh of relief when the season comes to a close. That relief is coupled with a deep understanding of why the same people keep coming back for more: Connecting to the community(社区) as you freely give your time, money, skills, or services provides a real joy. Volunteering just feels so good.

In that sense, I’m pretty sure volunteering is more of a selfish act than I’d freely like to admit. However, if others benefit in the process, and I get some reward too, does it really matter where my motivation lies?

2 . Bacteria are an annoying problem for astronauts. The microorganisms(微生物) from our bodies grow uncontrollably on surfaces of the International Space Station, so astronauts spend hours cleaning them up each week. How is NASA overcoming this very tiny big problem? It’s turning to a bunch of high school kids. But not just any kids. It is depending on NASA HUNCH high school classrooms, like the one science teachers Gene Gordon and Donna Himmelberg lead at Fairport High School in Fairport, New York.

HUNCH is designed to connect high school classrooms with NASA engineers. For the past two years, Gordon’s students have been studying ways to kill bacteria in zero gravity, and they think they’re close to a solution(解决方案). “We don’t give the students any breaks. They have to do it just like NASA engineers,” says Florence Gold, a project manager.

“There are no tests,” Gordon says. “There is no graded homework. There almost are no grades, other than ‘Are you working towards your goal?’ Basically, it’s ‘I’ve got to produce this product and then, at the end of year, present it to NASA.’ Engineers come and really do an in-person review, and...it’s not a very nice thing at times. It’s a hard business review of your product.”

Gordon says the HUNCH program has an impact(影响) on college admissions and practical life skills. “These kids are so absorbed in their studies that I just sit back. I don’t teach.” And that annoying bacteria? Gordon says his students are emailing daily with NASA engineers about the problem, readying a workable solution to test in space.

4 . Washington, D.C. Bicycle Tours

Cherry Blossom Bike Tour in Washington, D.C.

Duration: 3 hours

This small group bike tour is a fantastic way to see a world-famous cherry trees with beautiful flowers of Washington, D.C. Your guide will provide a history lesson about the trees and the famous monuments where they blossom. Reserve your spot before availability — the cherry blossoms—disappear!

Washington Capital Monuments Bicycle Tour

Duration: 3 hours (4 miles)

Join a guided bike tour and view some of the most popular monuments in Washington, D.C. Explore the monuments and memorials on the National Mall as your guide shares unique facts and history at each stop. Guided tour includes bike, helmet, cookies and bottled water.

Capital City Bike Tour In Washington, D.C.

Duration: 3 hours

Morning or Afternoon, this bike tour is the perfect tour for D. C. newcomers and locals looking to experience Washington, D.C. in a healthy way with minimum effort. Knowledgeable guides will entertain you with the most, interesting stories about Presidents, Congress, memorials, and parks. Comfortable bikes and a smooth tour route(路线) make cycling between the sites fun and relaxing.

Washington Capital Sites at Night Bicycle Tour

Duration: 3 hours (7miles)

Join a small group bike tour for an evening of exploration in the heart of Washington, D.C. Get up close to the monuments and memorials as you bike the sites of Capitol Hill and the National Mall. Frequent stops are made for photo taking as your guide offers unique facts and history. Tour includes bike, helmet, and bottled water. All riders are equipped with reflective vests and safety lights.

Some time after 10,000 BC, people made the first real attempt to control the world they lived     1     , through agriculture. Over thousands of years, they began to depend less on     2     could be hunted or gathered from the wild, and more on animals they had raised and crops they had sown.

Farming produced more food per person     3     hunting and gathering, so people were able to raise more children. And，as more children were born, more food     4    (need). Agriculture gave people their first experience of the power of technology     5    (change) lives.

By about 6000 BC，people     6     (discover)the best crops to grow and animals to raise. Later，they learned to work with the     7     (season)，planting at the right time and, in dry areas,     8     (make) use of annual floods to irrigate (灌溉) their fields.

This style of farming lasted for quite a long time. Then，with     9     rise of science, changes began. New methods     10     (mean) that fewer people worked in farming. In the last century or so, these changes have accelerated. New power machinery and artificial fertilizers (化肥) have now totally transformed a way of life that started in the Stone Age.

7 . At the start of the 20th century, an American engineer named John Elfreth Watkins made predictions about life today. His predictions about slowing population growth, mobile phones and increasing height were close to the mark. But he was wrong in one prediction: that everybody would walk 10 miles a day.

Today, in Australia, most children on average fall 2, 000 steps short of the physical activity they need to avoid being overweight. In the early 1970s, 40 per cent of children walked to school, while in 2010, it was as low as 15 percent.

The decline is not because we have all become lazy. Families are pressed for time, many with both parents working to pay for their house, often working hours not of their choosing, living in car-dependent neighborhoods with limited public transport.

The other side of the coin is equally a deprivation: for health and well-being, as well as lost opportunities (机会) for children to get to know their local surroundings. And for parents there are lost opportunities to walk and talk with their young scholar about their day.

Most parents will have eagerly asked their child about their day, only to meet with a “good”, quickly followed by “I’m hungry”. This is also my experience as a mother. But somewhere over the daily walk more about my son’s day comes out. I hear him making sense of friendship and its limits. This is the unexpected and rare parental opportunity to hear more.

Many primary schools support walking school-bus routes (路线), with days of regular,   parent-accompanied walks. Doing just one of these a few times a week is better than nothing. It can be tough to begin and takes a little planning-running shoes by the front door, lunches made the night before, umbrellas on rainy days and hats on hot ones-but it's certainly worth trying.