Everyone should make a contribution the environment.
| A．to protect | B．to protecting | C．protects | D．protected |
Tom found _____ difficult to learn chemistry well.
A.it B.that C its
Our English teacher said _____ English well was very important.
A.learn B.learning C.learned
—Don’t throw stones at the animals in the zoo.—_____.
A.No, I won’t. B.Yes, I will. C.Yes, I do.
The doctor warned my father _____.
A.to smoke B.not smoking C.not to smoke
—My aunt goes to climb mountains every Sunday. —Oh? But she _____ hate exercising.
A.used to B.was used to C.is used to