So far no life has been found outside the earth, but while some scientists are actively searching for living things in outer space, others firmly believe there ______.
| A. mustn’t be |
B. may not be |
C. can’t be |
D. won’t be |
She always come to our help when we get into trouble ____ she is very busy.
| A．since | B．once |
| C．even if | D．so that |
He has three brothers, ________is a doctor.
| A．all of them | B．all of who |
| C．none of whom | D．both of them |
As teenagers of the 21st century, we should be ready to _____ the challenge of society.
| A．put | B．do |
| C．make | D．meet |
The reason _____ they held a party was _____ it was Sue’s birthday.
| A．why; because | B．why; that |
| C．that; that | D．that; because |
--Why do you look pale today?
--I was very ________my mother’s illness. I stayed awake last night.
| A．concerned about | B．concerned with |
| C．concerned in | D．concerned to |