I should not have laughed if I ________ you were serious.
A. thought B. would think
C. had thought D. have thought
I should not have laughed if I ________ you were serious.
A. thought B. would think
C. had thought D. have thought
C 句意;如果我知道你是认真的,我就本不应该笑。根据句意可知,本句是与过去事实相反的虚拟语气,所以从句应用过去完成时。