1 . 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

2 . Researchers at CU Boulder have developed a wearable device that changes the human body into a biological battery. The device is stretchy(弹性的) enough that you can wear it like a ring, sport band or any other thing that touches your skin. It also taps into a person's natural heat-employing thermoelectric generators to change the body's internal temperature into electricity. "In the future, we want to be able to power your wearable electronics without having to include a battery," said Jianliang Xiao, an associate professor at CU Boulder.

The concept may sound like something out of The Matrix film series, in which a race of robots have enslaved humans to harvest their precious organic energy. Xiao and his colleagues aren't that ambitious: Their devices can generate about 1 volt (伏特) of energy for every square centimeter of skin space-less volt per area than what most existing batteries provide but still enough to power electronics like watches or fitness trackers.

Scientists have previously experimented with similar wearable devices, but Xiao's is stretchy, can heal itself when damaged and is fully recyclable-making it a cleaner alternative to traditional electronics. "Whenever you use a battery, you're depleting(消耗) that battery and will, eventually, need to replace it," Xiao said. "The nice thing about our device is that you can wear it, and it provides you with constant power."

Just pretend that you're out for a jog. As you exercise, your body heats up, and that heat will radiate out to the cool air around you. Xiao's device captures that flow of energy rather than let it go to waste. "The thermoelectric generators are in close contact with the human body, and they can use the heat that would normally be sent into the environment," Xiao said.

1. What does Xiao expect of his device at present?

A．It will be used for medical purposes.

B．It will be made smaller and wearable.

C．It will change natural power into electricity.

D．It will supply constant power to wearable devices.

2. Why does the author mention The Matrix series in the text?

A．To give an explanation.	B．To make a comparison.
C．To introduce a topic.	D．To analyze the cause.

3. What does the third paragraph mainly talk about?

A．The strengths of Xiao's device.

B．The convenience of using a battery.

C．The replacement of wearable devices.

D．The development of traditional electronics.

4. What do we know about Xiao's device from the text?

A．It operates with plenty of power.

B．It is designed for practical use.

C．It benefits people's health in a way.

D．It's based on traditional electronics.