What does she usually use the computer _________– She usually uses it to chat with her friends.

下列各句中，没有语病的一句是（ ）

He ________ sleep, although he tried to, when he got on such a hunt for an idea until he had caught it.

You promised your friend a letter; you ought to ______ days ago.

John went to the hospital alone.If he ________ me about it, I would have gone with him.