Exploring the polar regions is a _______ issue because it may destroy the ecological environment there.[ ]

下列各句中，没有语病的一句是（  ）

One reason for her preference for city life is ________ she can have easy access to places like shops and restaurants.[ ]

The boy didn’t sleep well last night because of the ______ from the factory.

How many birds can you see in the trees–I can see ________ birds in the trees.