What would you have done if you ___ the lottery last week?
b) 'd won
c) 'd have won
d) 'll win
The given answer key is (C).
I think both (b) and (c) are okay in this sentence, but I cannot make an absolute verdict.
In Michael Swan's Practical English Usage (3rd ed.), I find such entry.
What follows is quoted from entry 262.
What are your opinions about the answer(s) to the question?if: other structures found in spoken English
2 'd have ... 'd have
In informal spoken English, if-clause referring to the past are sometimes constructed with 'd have. This is frequently considered incorrect, but happens quite often in educated people's speech. It is not normally written.
The only correct answer is (b) 'd won.
The key to the answer(s) in your book must then be corrupted, I'm afraid.