The tree must ________ three times a week

I found a story-book on the desk,it isn’t mine, it is ___,I think.

The ticket ______ him ￥20.And flying to the USA ________him two days.

Having a trip abroad is certainly good for the old couple, but it remains ______ whether they will enjoy it.[ ]

The doctor thought ____ would be good for you to havea holiday