Which one is right of the

Which one is right of the following sentences?

2个回答

A.I don't think it is a free choice.（正确）
B.I think it is not a free choice.（think后面的宾语从句不用否定式.）
C.I didn't think it is a free choice.（前后时态不一致.）
D.I thought it wasn't a free choice.（think后面的宾语从句不用否定式.）