The date for the conference we had been looking forward_at last.A.to come B.to coming C.to came D.to have come

问题描述:

The date for the conference we had been looking forward_at last.A.to come B.to coming C.to came D.to have come

选C.
原句可以拆成如下的句子:
We had been looking forward to the date for the conference.
The date came at last.