—Must I turn off the gas after cooking?
—Of course.You can never be ________ careful with that.
| A．enough | B．too | C．so | D．very |
_______ the news of his father's death, he burst into tears.
| A．After hearing | B．On hearing | C．While hearing | D．Having heard |
I searched for my wallet and it wasn't there. At first, I thought I _______ it at home. Then I remembered _______ it out to pay for the taxi.
| A．must have left；to take | B．may leave；taking |
| C．might leave； to take | D．could have left；taking |
The thief drove as fast as he could to escape ________ by the police.
| A．to be caught | B．he caught | C．being caught | D．catching |
I delayed _______ your letter because I had been away for a week.
| A．answer | B．answering | C．writing | D．to post |
---Will the Smiths go abroad this summer?
---No, they finally decided _______.
| A．to | B．not going | C．not to | D．not to be going |