When I got on the bus, I_____ I had left my wallet at home.
| A．was realizing | B．realized |
| C．have realized | D．would realize |
. _______ his mother, the baby could not help _______.
| A．To see ；to laugh | B．Seeing ； to laugh | C．Seeing ；laughing | D．To see ；laughing |
_______ 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 |