下列词语中加线的字,每对读音都不相同的一组是(　　)

The letter she had been looking forward to _______ her yesterday.

You’d better ride a bike to go to school _____ takinga bus every day.

He was crazy ______ his study when he was young, which contributes ______ his success in later life.

Why does Maria look so tired—She missed our school bus, ______she had to walk here all the way.