Question

If you _____ him yesterday, you _____ what to do now.

1. A.
   asked … would know
2. B.
   had asked … would have known
3. C.
   asked him … know
4. D.
   had asked … would know

Answer 1

D
从句与过去事实相反用had done，主句与现在事实相反用would do。