20. The flu is believed________by viruses.
| A．causing | B．being caused | C．to be caused | D．to cause |
Mr. Bake is a professor of phsics; ____, he is a famous writer.
| A．in all | B．in brief | C．in fact | D．in addition |
I started into the darkness and wonderful if he was as_____my presence as I was of his.
| A．aware of | B．aware that | C．quite aware | D．very aware |
He has ____of the team.
| A．left out | B．left over | C．left alone | D．left off |
Though ____money, his parents managed to send him to university.
| A．lacked | B．lacking of | C．lacking | D．lacked in |
Those who steal books in the library _____ not be allowed to borrow any again in the future.
| A．shall | B．must | C．may | D．can |