Most whales must come up for air after several minutes, _______ a few can stay under water for an hour or more.
A．while B．or C．for D．so
The numbers that researchers get from the experiments can be _______, just like number puzzles.
A．disappointing B．inspiring C．worrying D．confusing
_______ the house is empty, memories flood my mind of a time when it was filled with life.
A．Since B．Unless C．As if D．Even though
By the time a child is five, he _______ hundreds of hours of television.
A．will watch B．will have watched C．had watched D．is watching
There is nothing wrong with using a credit card for purchases. It’s more _______ than carrying loads of cash.
A．convenient B．valuable C．sensitive D．innocent
An earthquake of 9 magnitude struck off the coast of Japan on Friday,______ thousands of people dead and more missing．
A．caused B．causing C．having caused D．to cause
