This everything will be the twenty-ninth time we _ the experiment.A.will do B.have done C.didD.are to do

问题描述:

This everything will be the twenty-ninth time we _ the experiment.A.will do B.have done C.did
D.are to do

选B。This everything will be the twenty-ninth time we have done the experiment.这将是我们第29次做这个实验。

【B. have done.】

这次是第29次,那么之前就发生过28次,连同这一次(说话的时候刚完成),就是说这29次都完成了.故用完成时态.