1 . Math holidays everyone should know

In recent years mathematicians and scientists have begun campaigns to mark certain dates in celebration of significant principles and here are a few to add to your calendar

Mole Day

Mole Day is celebrated yearly on Oct. 23 from 6: 02 a.m to 6: 02 p.m.. The idea of a celebratory day was put forward by a chemistry teacher in 1991 and has been honored every year since. It celebrates Avogadro's Number, which is a basic measuring unit in chemistry. Each Mole Day has a specific theme.

Pi Day

The grandaddy of mathematical and scientific holidays, however, falls every year on Mar. 14. The date, 3/14, represents the first three numerals in the calculation of pi, so the date is known annually as Pi Day.

Pi Day was founded in 1988 by a physicist. The observations spread to the point where on Mar. 12, 2009, the U.S. House of Representatives passed a resolution declaring Mar. 14 as National Pi Day.

Fibonacci Day

Nov. 23 marks Fibonacci Day, a special day that celebrates the man known as Fibonacci who developed a mathematical idea called the Fibonacci Sequence, in which every number is the sum of the previous two numbers. So, for example. 11/23 marks the day because 1+1 equals 2, and then 1+2 equals 3（the date being the 23rd）.

Square Root Day

Square Root Day is a holiday that heartily honors those dates where the combination of day and month and year form square roots: e.g. 2/2/04 and 3/3/09. The last Square Root Day was 4/4/16. The holiday was created by a high school teacher Ron Gordon. Square Root Day has its own website where celebrants can gather before the next holiday.

1. How is Mole Day similar with Pi Day?

A．They both have themes.	B．They are yearly holidays.
C．They fall on the same day.	D．They are created by a teacher.

2. Which holiday is to honor a person?

A．Mole Day.

B．Pi Day.

C．Fibonacci Day.

D．Square Root Day.

3. Which day might be celebrated as Square Root Day?

A．10/23/22.

B．11/23/23.

C．3/12/29.

D．5/5/25.

2 . China's historic 23-day Chang'e 5 mission has not only obtained precious rock and soil samples from the moon, but has also brought back a group of seeds that traveled the furthest in the nation's agricultural and forestry histories. More than 30 kinds of seeds, including that of rice, oats etc., were placed inside the multi-module Chang'e 5 spacecraft and orbited around the moon for about 15 days.

Scientists wished to check what would happen to the seeds after being exposed to extraterrestrial (地外的) forces in lunar orbit and also hoped that they could develop beneficial mutations (突变). This mission offered good opportunities to scientists, which enabled them to deepen their studies on the effect of cosmic rays on the growth and evolution of life on Earth.

Space-based mutation breeding refers to the process of exposing seeds to forces such as microgravity, vacuums and cosmic radiation during a spaceflight and then sending them back to Earth for further observation and planting. Researchers observe and examine several generations of plants grown from space-bred seeds and investigate their mutations-some are positive and desirable while others are negative. Those with positive mutations will be kept and analyzed, and will be introduced to farmers after their certification and approval.

Space breeding can generate mutations faster and more conveniently than ground-based experiments and can bring about some desirable traits that are otherwise hard to introduce. Compared with natural or conventionally bred types of plants, space-developed versions with positive mutations usually feature higher nutritional content, greater annual yields, shorter growth periods and better resistance to diseases and insect pests.

China conducted its first space breeding experiment in 1987, using a satellite to carry seeds into space. Since then, hundreds of kinds of seeds and seedlings have traveled with dozens of Chinese spaceships. Space breeding has helped to produce more than 200 new types of mutated plants in China that have been approved for large-scale cultivation, ranging from grains to vegetables and fruits. The Chang'e 5 robotic mission returned 1,731 grams of lunar rock and soil to Earth, marking a historic accomplishment 44 years after the last lunar substances were taken back.

1. Why were the seeds placed inside Chang'e 5?

A．To pick out the fittest for mutations.	B．To understand extraterrestrial forces.
C．To study the intensity of cosmic rays.	D．To expose them to a special environment.

2. What do we know about space-based mutation breeding?

A．It is not a time-consuming process.	B．Mutations develop in a random way.
C．It often brings about desirable effects.	D．Approval will be granted to mutated plants.

3. What can we learn from the last paragraph?

A．It is a custom to put seedlings on a spacecraft.

B．China was the first to do a space breeding experiment.

C．It is some time since seeds were last taken into space.

D．Space breeding has brought us commercial benefits.

4. What is the best title of the passage?

A．Space-bred Seeds Offer Great Chances	B．Chang'e 5 Returns with a Big Package
C．Plant Mutations Result in a Better Life	D．Seeds from Space Mark a New History

3 . If all goes well, a balloonwill soon rise from Esrange Space Center in Kiruna, Sweden. It will float highinto the upper atmosphere and then return to Earth. However, environmentalists have arrived to stop this from happening.

The campaigners are against the balloon because of what occurs in flight. The balloon will shoot dust into the Earths upper atmosphere, causing more sunlight to reflect back into space. The dust, known as stratospheric aerosolinjection(SAI), is part of a solar geoengineering (地球工程) program named SCoPex which is being conducted by Harvard University. The aim of the program is to purposely change the Earth's atmosphere to fight climate change.

Those who oppose worry about two things. Firstly, the moral risk-if solar geoengineering works, talks on reducing greenhouse gases will be challenged. The second concern is the amount of SAI in the atmosphere. To keep temperatures low, the need of the reflective dust tobel released high above Earth will be endless, and a sudden stop could result in rapid warming. Raymond Pierrehumbert, a physicist at Oxford University, says solar geoengineering is even tool risky to research beyond computer models.

Not all environmentalists are opposed to it. Since the world is unlikely to achieve the 1. 5 ℃ global warming target set in the Paris Agreement, some green organizations favour small-sized geoengineering research.

Regardless of the criticism, the research continues. Geoengineering is increasingly gaining international attention. A recent report about climate change suggested that SAI could help keep warming below 1. 5℃. The National Academy of Sciences, Engineering and Medicine in the USA has developed a research plan for solar geoengineering and received governmental funding totaling $9 million. Both China and India have also launched research programmes of their own. Activists may oppose the experiments, but balloons will likely fly anyway.

1. What is the function of SAI?

A．To attract dust.	B．To throw sunlight back.
C．To absorb heat.	D．To fight against pollution.

2. Why does Raymond Pierrehumbert say geoengineering is risky?

A．It may change computer models.

B．It may produce too much dust.

C．It may release greenhouse gases.

D．It may worsen global warming.

3. How do some people expect geoengineering research to be done?

A．To a limited degree.

B．At a lower temperature.

C．By green organizations.

D．Without international attention.

4. Which of the following can be inferred?

A．Voices of environmentalists are ignored.

B．More support is going to geoengineering.

C．Global warming is getting worse in Sweden.

D．Geoengineering has proved effective in India.