Please Listen to the following TED talk and answer the questions followed.(1分11秒-55秒）

What happened when the speaker just built the instrument with his team to propose an experiment to fly to Venus?

A.He just joined NASA

B.He became involved in calculations of the greenhouse effect on earth and found that our atmospheric composition was changing

C.He has just resigned as principal investigator on the Venus experiment

D.He was continuing his experiment on the trip to Venus

正确答案：He became involved in calculations of the greenhouse effect on earth and found that our atmospheric composition was changing