He _____ have completed his work; otherwise, he wouldn’t be enjoying himself by the seaside.
| A．should | B．must | C．wouldn’t | D．can’t |
The graduating students are busy _______ material for their reports.
| A．collect | B．to collect | C．collected | D．collecting |
I had to shout to make myself _______ above the noise.
| A．heard | B．hearing | C．heard | D．to hear |
.He walked down the hills, _______ softly to himself.
| A．sing | B．singing | C．sung | D．to sing |
.At this moment the bell rang _______ the end of class.
| A．announce | B．announcing | C．announced | D．to announce |
The child sat in the dentist's chair _______.
| A．tremble | B．trembling | C．trembled | D．to trembled |