One astronaut who joined the program in 1996 ______ only after

One astronaut who joined the program in 1996 ______ only after he had been applying for 12 years.
A、 has been accepted
B、 had been accepted
C、 was accepted
D、 is accepted
【正确答案】：C
【题目解析】：该题考查的是过去时态，only after从句用过去完成进行时表示事件持续发生了12年之后，事件发生在过去并且有具体的时间，因此选项C为正确答案。