下列各句中，没有语病的一句是(　　)

You may find the key to the maths problem on page 107—Ah, it’s so simpleI wonder why I ________ of that

Whenafire______attheNationalExhibitioninLondon,atleasttenpricelesspaintingswerecompletelydestroyed.

Gun control is a subject ________ Americans have argued for a long time.

The patient is not out of danger. He is ________ than he was yesterday.