Some scientists think     1     idea of people living on Mars will come true one day. Stephen Hawking believed humans must move into space to survive. “Once we spread out into space and establish     2     (dependent) colonies, our future should be safe,” he said, Robert Zubrin, a rocket scientist, agrees and thinks starting with Mars     3     (make) the most sense. He thinks sending people to Mars will allow us to learn a lot--for example, about the ability of humans to live in a very different environment.

However, scientists will need to terraform Mars for people to be able to live. Terraforming means changing the environment on a planet so that it is similar to Earth's. One of the main goals of terraforming Mars is to warm it up     4     the average temperature there is about -60°C. One idea for warming Mars is to build factories there     5     produce greenhouse gases. This could take many     6     (century). However, it should lead to rainfall and the growth of plants,     7     (result) in more air that people can breathe.

Another big concern for scientists is whether humans can move to Mars and still live     8     (healthy) in mind and body. Not to feel bored, humans on Mars would always need to keep     9     (they) busy with various activities. And the people living together should all be able to get     10     and work together.

China's BeiDou Navigation Satellite System (BDS) has played a     1     (significance) role in the country's flood-control operations, said BDS spokesperson Ran Chengqi. The BDS system has helped the country fight against floods,     2     (assist) in early warning and resident transfer, Ran said.     3     (base)on its ground stations, the BDS system can provide high- precision services with centimeter-level     4     (accurate) in real-time processing.

In July, 2020, in Shimen County, Hunan Province, the BDS monitoring system     5     (help) issue early warnings and relocate over 60 people threatened by a landslide, thus ensuring   the safety of people's lives and property.

Another great function of the BDS system is short message communication, which allows users     6     (send) messages without the support of a mobile network. The short message communication capability of the BDS-3 system has been greatly improved. Users can send a message of 1,000 Chinese characters at one time.

The BDS system can also aid international search and rescue with its bidirectional communication services. Ships     7     need of rescue can receive a reply from the ground station after sending an emergency signal,     8     is a more advanced method than those used previously. China will try to provide legal support and policy guarantees and create     9     sound, open environment for the development of the BDS system. The combination of BDS with advanced technologies, including 5G, mobile communications and big data, will be     10     (far) promoted to create new business models and growth points.

This year marks     1     20th anniversary of China’s first manned space mission(任务)that sent astronaut Yang Liwei on a 21-hour journey around Earth in the Shenzhou V spacecraft. As one of the     2    (nation) in the world able to independently finish manned space missions, China     3    (carry) out 12 manned flights since then.

A special committee was formed in August 1992 and it     4    (decide) that China would use manned spacecraft to build a space station in the coming years. The plan was passed in September that year,     5    (mark) the first official manned space program of the nation.     6    (achieve) the goal, scientists made specific plans and took practical steps, advancing slowly from multi-day flights     7     month-long missions. Thanks to years of efforts, we are proud that our country completed the Tiangong space station last year. Orbiting Earth about 400 kilometers above the ground, Tiangong has both a core module     8    two science facilities, which is     9    (regular) connected to several visiting spaceships.

Chinese researchers are designing a new-generation manned spacecraft,     10     will be significant in the nation’s first manned exploration to the moon around 2030.