We ___________ try our best to fight against pollution.（ ）
| A． |
should |
B． |
may |
C． |
mustn't |
D． |
needn't |
﹣﹣﹣Are these books_______？
﹣﹣﹣No，they're his.（ ）
A．yoursB．herC．ourD．their
﹣﹣﹣What did the teacher say just now？
﹣﹣﹣He told us________in the river.（ ）
A．swimB．swimming
C．not to swimD．not swim
﹣﹣﹣What' s your favorite_______ ，John？
﹣﹣﹣History.It is very interesting.（ ）
A．foodB．vegetableC．animalD．subject
William six books，and all of them are bestsellers.（ ）
A．will writeB．is writing
C．has writtenD．was writing
These gifts by children in their last summer holidays.（ ）
A．madeB．were madeC．makeD．are made