单项选择题
A B
A.be living in the United States B.have Ph.D. degree C.have stock share D.have more than 10 years in a business environment
A.U.S. professors B.former student participants C.UN senior staff members D.UN professors
A.In the middle of summer on Earth. B.In the middle of summer on Mars. C.In the middle of summer on Earth’s polar caps. D.In the middle of summer in the northern part of Mars.