Fill in the blanks with suitable words according to the meanings in the brackets.

1. His father used to be a ________ (high in rank or position) officer in the Liberation War.

2. Before the speaker began the lecture, he gave a ________ (a movement of hand as part of communication)

    for everyone to become quiet.

3. I was given some ________ (help) in coming to my decision.

4. He said nothing, but his facial ________ (a look on one's face that communicates feeling) told us everything.

5. _______ in class is the key to efficient(有效率的)study. (thinking deeply about something)

水准仪望远镜只能绕竖轴水平方向转动。