Dr. Black comes from either Oxford or Cambridge. I can't remember______.

A . one B . a C . –（不填） D . the

A . simply B . only C . just D . eve

A . proper fuel injection B . water in the fuel C . incomplete combustion D . burning of lube oil

A . fuel dribbling from leaking fuel injectors B . burning fuel with a high carbon content C . burning fuel with a high vanadium content D . burning fuel with a lower sulphur content

A．ranges B．constitutes C．composes D．consists

W：I am afraid not．This book has been put on reserve Dr．Black，Unless you have his written permission，we won't let it out． Q：What should the man do to borrow the book？ (16) A．Get Dr. Black's written permission. B．Ask Dr. Black to call the library. C．Get the book directly from Dr. Black. D．Ask Dr. Black to change his decision.

A．China. B．America. C．Australia.

According to Dr. Scorer, Benjamin Franklin first proved thunderclouds are charged with electricity. Later investigation showed that the tops of the clouds have a great positive charge and the bottoms a great negative charge. When the charges become great enough to break down the insulating properties of the air, lightening flashes carry the electricity within the cloud, or from cloud to cloud, or from cloud to earth. But the question remained: how do the charges develop within the cloud？ To seek the cause, Dr. Scorer and his colleagues at the college first duplicated thundercloud currents in a liquid tank. They doubt that mixture takes place only in the tops of the clouds. Next a study of thunderclouds over the North Atlantic showed that lightening occurs only when the air temperature around the cloud is below freezing. Particles at the top of the cloud begin to freeze, but those in the remainder of the cloud stay unfrozen although below freezing temperature. To measure moisture, the scientists sent planes equipped with external refrigerated rods into the clouds. The idea was that moisture would freeze on the rods and could later be measured. The men found, however, that some of the moisture particles bounced off the rods. This accidental discovery set the scientists on a new course of action. In the laboratory, S. E. Reynolds whirled a refrigerated rod through ice particles and found that the particles bounced off the rod acquired a positive charge. This was the missing link. Without hail and super-cooled clouds, he concluded there could be no lightening. According to the article, Benjamin Franklin was the first to prove that _______. A．lightening is caused by hail falling through super - cooled clouds B．thunderclouds are not charged with electricity C．thunderclouds are charged with electricity D．lightening was not an invention of the devil

A．since B．when C．before D．after

A．Shakespeare B．Bacon C．Shelly D．Marlowe