Our bad living habits will destroy the earthOnly by changing________we live can we save the earth

It is required that the students ________ mobile phones in their school, so seldom ________ them using one.[ ]

If it ____ tomorrow, I ____ not go there by bike.

Looking out of the window of my room, ___ atall tree in the yard.

dges gave no hint of what they thought, so Ileft the room really ________