If John had entered the office ten minutes ago, he () what we we

If John had entered the office ten minutes ago, he () what we were talking about just now.
A、should know
B、had known
C、would know
D、would have known
【正确答案】：D
【题目解析】：句意：如果约翰十分钟前进办公室，他就会知道我们刚才在说什么了。本句为引导的虚拟条件句，根据从句中的时间状语ten minutes ago可知，该句表示与过去事实相反的假设，因此条件从句的谓语用过去完成时(had +过去分词)，主句谓语用“should/would/could/might +have+过去分词”，故选D。