He had some trouble, but he kept on_______________ and didn’t give up.

On each side of thestreeta lot of trees.

Our playground is not so tidy and beautiful as before,students must ____ dirty things on it.

If we_________ sunlight_________ a dry leaf with a piece of glass, it may start burning.

The physics exam is not difficult, is it?-________. Even Tom ________ to the top students failed.[ ]