Experiments of this kind___in both the U.S. and Europe well before the Second World War
| A．have conducted |
| B．have been conducted |
| C．had conducted |
| D．had been conducted |
With all his money, he _____worry about a little thing like 5 cents!
| A．can | B．must | C．may | D．should |
_____we move the couch over there? Don’t you think the room will look larger?
| A．What about | B．How far | C．What if | D．How come |
—Who do you guess I am?
—Sorry, your name _____my mind.
| A．slipped | B．has slipped | C．was slipped | D．slips |
Stand over there _____you’ll be able to see it better.
| A．if | B．but | C．or | D．and |
Please refer to the before you switch on the engine.
| A．introductions | B．explanations | C．instructions | D．expressions |