These natural parks are very important for preserving many animals, which would _______ run the risk of becoming extinct.
| A．otherwise | B．therefore | C．nevertheless | D．however |
He was heard________ three songs in the next room.
| A．sing | B．to sing | C．singing | D．sung |
-Young man, come off the grass; we forbid________ on the grass here.
-Sorry, I didn’t notice it.
| A．to stepping | B．stepping | C．why | D．which |
Christina wasn’t saying anything, but the professor smiled at her _______she had done something very clever.
| A．as if | B．now that | C．while | D．though |
No matter what I do, my efforts ________always end in failure.
| A．lose weight | B．to lose weight | C．losing weight | D．lost weight |
The factory used 65 percent of the raw materials, the rest of which _____ saved for other purposes.
| A．is | B．are | C．was | D．were |