Mr Huang told us to spend as much time as possible ________ our English studies. [ ]

He is very tired，so he needs some time __________ duty for relaxation and rest．

I was giving a talk to a large group of people, the same talk I _____ half a dozen other groups before.[ ]

26I called _____ you last night, but you were out

It’s a pity that his son was born ________ a weak heart.