Hi,
4.C A
5.B D is the best answer
One more question. Is it normally after a sentence started with 'If I ..it should be appeared in past participle form? Depends onthe rest of the sentence.
eg If I had won the lottery, I would have bought a house.
eg If I win the lottery, I will buy a house.
eg If I won the lottery, I would buy a house.
Best wishes, Clive