The air pollution is so terrible.–It will be worse we do something to protect the environment.

Everyone should _______________ the environment.

The parents were in search _______ theirson who was lost when the two countries were ______ war.

下列文学常识的表述不正确的一项是（ ）

Are you willing to live on Mars（火星） one day— ______________ It sounds exciting, but it still worries me.