用所给动词的正确时态填空

1. It takes about an hour _______(go) to Changzhou by bus.

2. He left home without _______(tell) his mother.

3. My sister seldom _______ (play) volleyball now .

4. Look ! Lily's cat _______ (lie) on the sofa comfortably .

5. It's time for us _______(exercise) now.

6. I am planning _______ (take) a holiday to the USA.

氢气冷却系统正常运行时，发电机内氢气纯度按容积计应在（）以上。

A.90％

B.95％

C.96％

D.98％