【题目】At college, Barack Obama didn't know that he the first black president of the United States of America.
A.was to become
B.becomes
C.is to become
D.became

【答案】A
【解析】句意：在大学的时候，奥巴马不知道他将成为美国第一个黑人总统。用过去将来时表示过去某个时间将要发生的事情，所以选A。