________to strong sunlight for a long time will do harm to our skin.[ ]

Since drinking water is a limited resource, we ________ let children know how precious it is, and teachthem to conserve it.[ ]

Excuse me, but can I sit here— ________. The man who sat here says he will be back soon.

Tens of thousands of people had ___outside the US embassy.

Sorry, I have to ________ now. It’s time for class.—OK, I’ll call back later.