We have to______the costs of the new system against the benefits it will bring.
| A．compare | B．weigh | C．judge | D．consider |
Many scientists believe that global warming , if , will cause extreme climate changes this century .
| A．not stopping | B．no stop | C．not stopped | D．without stop ycy |
John did quite well in his exams ,how little he studied .
| A．consider | B．considering | C．considered | D．to consider |
Although there is no life on Mars now , some scientists think that there some form of life a long time ago .
| A．must be | B．may have been | C．can have been | D．could be |
They were playing in the garden they heard a scream .
| A．while | B．as | C．until | D．when |
Many people in this country eat as they actually need every day.
| A．twice as much meat | B．twice meat as much |
| C．as twice much meat | D．meat as much twice |