Though I was tired out that evening, I _____ from falling asleep by the great pain in my knee.
| A．was prevented | B．had prevented | C．has prevented | D．am prevented |
The sign reads “In case of ____ fire, break the glass and push ____ red button. ”
| A．不填；a | B．不填；the | C．the; the | D．a; a |
Seeing the soldiers well _____ for the flood-fight, the general nodded with satisfaction.
| A．prepare | B．preparing | C．prepared | D．having prepared |
Mr. Green is said _____ an experiment to prove the new method of solving the problem when young.
| A．to do | B．to have done | C．to be doing | D．to have been doing |
—— Have you considered _____ your job as a teacher?
——Yes. I like the job because a teacher is often considered _____ a gardener.
| A．to change; to be | B．to change; being | C．changing; being | D．changing; to be |
The monument was built in honor of the explorer who was believed _____ the river.
| A．to have discovered | B．to have been discovered |
| C．to discover | D．having been discovered |