He raised one arm and then the other.

　　他先舉起一只手，然后舉起另一只。

　　I've never heard him even raise his voice.

　　我甚至從沒聽到他提高過嗓門兒。

　　I'm sure she's keeping something back from us.

　　我肯定她有什么事瞞著我們。

　　Some teachers find it difficult to keep their classes in order.

　　有些教師覺得難以維持課堂秩序。