—Who______ it be that is knocking at the door?
—It ______ be Father, but I’m not sure.
A. can; must B. can; may C. must; can D. may; must
Once harm is _______ to the eco-system, all species will ________, including man himself.
A. made; be in danger B. done; be dangerous
C. caused; be endangered D. done; be in danger
The stamp on the letter is an art, from _______ we can get a lot of cultural knowledge.
A. whom B. which C. them D. those
It is believed that a new kind of drug ______ by the scientists and they are hopeful that they will succeed in a few months.
A. has been developed B. is being developed
C. is developing D. has developed
Jenny nearly missed the flight ________ doing too much shopping.
A. as a result of B. on top of C. in need of D. in front
If you receive a bunch of roses on Valentine’s Day, do you know what hidden meaning is _______ to it?
A. put B. introduced C. attached D. tied
