You can try outdifferent ways,and______they are helpful,you

You can try outdifferent ways,and______they are helpful,you can use them.
A.only if B.if only C.as if D.what if
2.The new edition of the textbook is about_______the old one.
A.the price of twice B.twice the price of C.twice of the price D.twice price of
3.Will mary become the next manager?
No,____the boss appreciates mary's ability,he doesnt like her character.
A.But B.As C.When D.While