.MrRichard hasn’t got any time to play golf these days,because he is ______in the research of bird language

He is taller than he______.

I’m afraid you’ll have some problems________your health.

Mr. Hall understands that _______ math has always been easy for him, it is not easy for the students.

﹣I’m sorry I ________ my exercise book at home this morning．﹣It doesn’t matter．Don’t forget ________ it here this afternoon．