____ the 1990s, the number of antelopes had fallen to about 50,000.
A．During B．Since C．By D．Over
If the machine makes a mistake -- ____ rarely happens -- it gives a warning in the form of a red light.
A．that B．which C．as D．what
J.K. Rowling, ____ gifted creator of Harry Potter, is ____ success in the literary world.
A．a; a B．\; a C．the; \ D．the; a
______is estimated that a round-trip to Mars would take more than a year.
A,That B,what C,There D,It
______leaves the room last ought to turn off the lights.
A,The person B,whoever C,Who D,Anyone
The reason why he was removed was ______he was careless and dishonest.
A,when Bbecause C,that D,what
