What a pity! Considering his ability and experience，he___ better．
| A．need have done | B．must have done | C．can have done | D．might have done |
No scientists can exactly figure out what ________ happened ________ at that time, which caused the extinction of the dinosaurs.
| A．on earth; on the earth |
| B．on the earth; on earth |
| C．on earth; on earth |
| D．on the earth; on the earth |
Experiments of this kind ________ in both the U.S. and Europe long before the Second World War.
| A．conducted | B．was conducted |
| C．had been conducted | D．had conducted |
-- Shall we take a taxi there since time is limited?
-- ________. It should be hard to get one during the rush hour.
| A．Go ahead | B．Don’t mention it |
| C．No doubt | D．Just forget it |
Traveling without ordering rooms in advance can eat up precious vacation time ________luck is smiling on you.
| A．unless | B．as | C．if | D．when |
-- It’s more convenient to take a subway than drive a private car.
-- ________. What’s more, it’s also a good way to support the low-carbon lifestyle.
| A．Quite so | B．So is it |
| C．By all means | D．All right |