----When will the expert come and give the lecture on intell

----When will the expert come and give the lecture on intellectual property?
----Not until our program____by the authorities.
A.approves B.has been approved C.is to approve D.will be approved
选【B】,has been approved
【专家什么时候来作关于知识产权的讲座?
直到我们的方案被权威机构认可才可以.】
用【现在完成时】是因为：
权威机构认可我们的方案是从过去就开始的,直到现在还没结束,即一直持续到现在,对现在或将来还有影响,所以用现在完成时.
完整答语应该是
Not until our program has been approved by the authorities will the expert come and give the lecture on intellectual property.
not until 打头,句子用倒装结构.
我的疑问是：对现在或将来还有影响,为什么就用现在完成时?还有完整答语怎么得来的?我该怎么做这种省略句呢?