24. 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
用过去将来时表示过去某个时间将要发生的事情，故选项A符合答案。
根据句意：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。
对过去将来时的表达不熟悉。