Question

if you (work)__ harder last year,you would have passed your exam

Answer 1

had worked
本题考查if虚拟语气中的用法。此题中有从句我已经通过了考试（would have passed ），表明从句是过去时，故对过去进行虚拟
全句话的意思就是我要是再努力一点，就通过考试了。由于此题中，主从句的主语都是一样的，故用Had you worked
if虚拟语气和if引导从句的一般将来式的区别如下
if引导条件状语从句的时候，我们分为两种情况，一种是真实的条件，一种是假设，叫作非真实条件状语从句

当IF引导真实条件状语从句，就要遵循我们所说的主将从现的原则，即主句用一般将来时，从句用一般现在时，比如 If all goes according to plan, the first concert will be Tuesday evening.这个就是真实的。

当IF引导非真实条件状语从句时，就要用虚拟语气表达。
1。if + 一般过去时，与现在事实相反，if i were a bird ,i would fly out of the school.
2. if + should/could/would +do，与将来事实相反，if i would finish the job tomorrow, i will call you.
3. if + had done ,与过去事实相反，if i had asked you how to do it ,i would not have made such a fool mistake.

怎么区别，就是看从句的时态，在根据语境判断。

Answer 2

had worked

这是一个标准的对过去虚拟的虚拟句

主句是would 加完成时，从句用过去完成时，是表示对过去的虚拟

Answer 3

答案

had worked