Lots of the scientists in our country are working hard to the planet Mars .A. coverB. sear

问题补充：

Lots of the scientists in our country are working hard to the planet Mars .

A. cover

B. search

C. discover

Dexplore

答案：

A. cover

B. search

C. discover

(答案→)D. explore

解析：动词词义辨析。A覆盖；B搜寻；C发现；D探索；句意：我们国家的很多科学家都在努力工作致力于探索火星。根据句意说明D正确。