To pick up as soon as possible, Tom was advised to do exercise ________ a change in diet.[ ]

This special strain of rice makes _________ possible to produce one third more of the crop in the same fields.

Tom finished his homework, didn’t he—__________, though he was ill yesterday.

___he hasn’t come is_______ he is busy writing his novel

Jackson has got to be crazy ________Chinese culture since he visited China last time.