大学英语：as if

He looked at me as if I were mad.

She opened her eyes as if conscious of my gaze.

He works so hard as if he never knew fatigue.

14. have one's wits about one〔机警，保持警觉〕

In this part of the city you have to have your wits about you all the time.

He felt it unnecessary to have his wits about him on such a friendly occasion.

15. a variety of

Don't bother him， he has a variety of duties to perform.

The college library has a wide variety of books.

16. difference between

Will you please tell me the difference between the two countries?

I cannot see any difference between the two oil paintings.