Humans have always had a natural curiosity about space. Long before the mid-20th century, many scientists     1     help humans realize their dreams. And space travel became a reality with the success of American and Soviet space missions. Mankind is exploring space in the hope of     2     more about the universe. Space travel has always involved great risks. One of the most dangerous parts of space exploration is helping people to escape the earth’s gravity. If something goes wrong during the launch, it can     3     an accident that kills everyone on board. Despite the huge risks, scientists     4     exploration. So far, China     5     in space exploration, becoming   the third country to send humans to space. The future of space exploration looks bright as many countries are planning further missions.

When the writer was enjoying the beauty of Tibetan antelopes(藏羚羊), he     1     the terrible times they experienced. In the 1980s and 1990s, hunters were shooting Tibetan antelopes to     2     by selling their valuable fur. Besides, their habitats were becoming smaller as new roads and railways were built. As a result their population     3     more than 50%.

In order to save this species from extinction, the government placed it under national protection. People     4     the antelopes day and night to keep them safe from attacks. Furthermore, bridges and gales were added to let antelopes move easily and keep them safe from cars and trains. With all the above measures taken, in 2015, the Tibetan antelope     5     the endangered species list.