Lucy is the________ of the twins, and she isthe_______ girl in her class.

Whatever the cause of the heat may be, we do know that the earth gets hotter down we dig.

It is ______ for children to learn to take care of themselves if they are going to camp for two weeks by themselves. [ ]

下列各句中，没有语病的一项是（ ）

The fog and haze(雾霾) in Beijing is getting worse and worse.— How terrible! We should try our best to protect the ___________.