The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.
| A.what | B.which | C.that | D.though |
The chairman thought _______ necessary to invite Professor Smith to speak at the meeting .
| A.that | B.it | C.this | D.him |
------Flight 302 to London_______ until 7:30 tomorrow morning.
-----No wonder I hear so many complaints from the passengers.
| A.has been delayed | B.delay | C.delayed | D.will be delayed |
When the American constitution ______into effect in 1789,it didn’t contain any words guaranteeing the basic rights of ordinary citizens.
| A.went | B.had gone | C.has gone | D.was going |