In January , 2004, the United States successfully launched “Spirit”, a Mars Exploration Rover, a new milestone in the history of mankind.
A. it marked
B. marking
C. marked
D. to mark
网友回答
A. it marked
(答案→)B. marking
C. marked
D. to mark
解析:题意为“2004年1月,美国成功地发射了“勇气”号火星探测器,标志着人类历史上一个新的里程碑”。