On September 11, 2001, Omar Eduardo Rivera, a blind computer technician (技术员), was working on the 71st floor of the World Trade Center with his guide dog     1     (name) Dorado. When the hijacked (被劫持的) plane hit the tower, Rivera knew     2     would take him a long time to escape from the building, but he wanted his lovely dog to have a chance     3     (get) out so he set him free in the crowded stairwell. “ I thought I was lost forever — the noise and the heat were     4     (terrify) — but I had to give him the chance of escape. So I touched his head, gave him a push and ordered him to go,” Rivera said.

The dog     5     (immediate) disappeared into the crowd, but a few     6     (minute) later Rivera felt the dog feeling his legs. Dorado came right back to his side and a co-worker     7     (bring) by him as well. Then Dorado and the selfless co-worker     8     (help) Rivera climb down 70 flights of stairs,     9     took nearly an hour. No sooner had they escaped from the building     10     it fell down completely, and Rivera says he owes his life to his faithful dog.

Hummingbirds (蜂鸟) are the smallest birds in the world. Researchers have spent three years     1     (study) hummingbirds to find out whether they can distinguish between spectral (光谱) and non-spectral colors.

A newly     2     (publish) paper has confirmed that these incredible tiny     3     (creature) indeed have the ability to tell the difference between these color types and that they can see colors completely unknown to the human eye.

Hummingbirds are one of nature’s wonders — they live     4     a diet containing high levels of sugar (and sometimes insects), they are almost     5     ( constant) on the move, and they can see colors that humans can’t even imagine.

There are four color cone types in the eyes of hummingbirds,     6     humans only have three color cone types. Although it doesn’t seem like     7     big difference, when it comes to seeing color, that fourth color cone type matters most. Hummingbirds wouldn’t have the ability to see non-spectral colors if it     8    (be) not for it.

To find out how hummingbirds see color, the research group set up work stations at the Rocky Mountain Biological Laboratory (RMBL) in Colorado where they     9     (train) wild broad-tailed hummingbirds to actively take part in their experiment.

The group was careful to keep     10     (they) work environment as natural as possible for the birds over the course of the three years when they worked on this.

It’s a wildlife expedition (远征) that has captivated (使着迷) the globe: a herd of 16 elephants trekking (跋涉) more than 300 miles from their home in Xishuangbanna National Nature Reserve. The herd’s trek began in March last year when 16 elephants     1     (see) moving from the reserve. Nobody is clear why the herd set out on this unprecedented (前所未有的) trek. Some suggest environmental degradation may have pushed them;    2     believe they are simply lost. An expert in elephant psychology believes that they likely left because of habitat loss and increasing human disturbance,    3     may have led to decreasing availability of food and water.

“We can’t ignore the effect of rapid development of the local economy on the loss of wildlife habitat,”    4     well-known expert on Asian elephant migration wrote on his Weibo page. “Clear waters and green mountains are as     5     (value) as mountains of gold and silver. A healthy and complete ecosystem is the cornerstone of sustainable economic development.

China’s wild elephants     6     (double) in number to more than 300 since the 1990s, but their habitat has shrunk     7     nearly two-thirds over the same period. Though China has extremely harsh penalties for those     8     (catch) killing elephants, the combination of these factors     9     (mean) that the potential for human-elephant conflict will only rise. It’s     10     (extreme) challenging for them to coexist.

The big fear is that the intensity of conflict between humans and elephants can start as just a nuisance and quickly grow to the point where people or elephants get killed.

Glass recycling has become such a big industry that the amount of glass     1     (recycle) is not meeting the demand for new glass to be produced. Some states in U. S. have attempted to resolve this situation in hopes of encouraging the     2     (produce) of glass over plastic by offering monetary incentives (奖励) for glass. For example, California has a special program     3     you can earn five cents for most glass bottles as well as plastic ones and aluminum cans less than 24 ounces. For items over 24 ounces, you can earn 10 cents each.