The meeting -----when Mr.Wang -----to school.A has begun; ge

The meeting _____when Mr.Wang _____to school.A has begun; get B has been on; get C had begun; got
为什么选C,不能够选D呢,还有,整个句子发生在现在不行么,从哪看出来一定是发生在过去的?
D.D had been on; got