The police stillhaven’t found the lost child, but they’redoing all they____.[ ]

Do you think it true that all the theories should ________ facts?-I don’t suppose so. If so, there would be no predictions(预言) [ ]

This summer, my family has decided to go _____ in North China to enjoy our holiday.

It is amazing that the little boy can swim ______the river ______100 meters wide

She hardly ever speaks English because she is afraid ________ mistakes _______grammar.