（）, we kept removing the pistons.

A . scavenging action of the piston B . piston type vacuum pump taking suction off a differential manometer C . gland exhausting manometer D . crankcase exhaust fa

A . cleanup B . uninstall C . deinstall D . reject

A . in itself B . to itself C . by itself D . of itself

A、back B、up C、off D、all

A . gravity B . viscosity C . density D . humidity

A . in contact with the fill opening to guard against static spark B . from making contact with the fill opening to guard against static spark C . in contact with the fill opening to allow proper venting D . None of the above

A . midnight B . noon C . beginning of the watch D . any convenient time

A . safety valve B . blow down valve C . scum valve D . feed check valve

A . burnt B . burning C . burn D . to bur

A . load B . substitute C . conservation D . reserve

A . In master's cabin B . In third office's cabin C . In a break-glass-type enclosure conspicuously located adjacent to the room D . In a locked locker conspicuously located adjacent to the room

A . cleanup B . commit C . deinstall D . reject

A、<p>1 only</p> B、<p>1 and 2 only</p> C、<p>1,2 and 3 only</p> D、<p>1, 2 3and 4</p>

A．consume B．complain C．concern D．claim

A．confident B．secret C．flexible D．positive

It is the same in history. Many things have been forgotten because we do not have any written account of them. Sometimes men did keep a record of the most important happenings in their country，but often it was destroyed by fire or in a war. Sometimes there was never any written record at all because the people of that time and place did not know how to write. For example, we know a good deal about the people who lived in China 4, 000 years ago, because they could write and leave written records for those who lived after them. But we know almost nothing about the people who lived even 200 years ago in central Africa because they had not learned to write. Sometimes, of course, even if the people cannot write, they may know something of the past. They have heard about it from older people and often songs and dances and stories have been made about the most important happenings, and these have been sung and acted and told for many generations, for most people are proud to tell what their fathers did in the past. This we may call ？remembered history ” . Some of it has now been written down. It is not so exact or so valuable to us as written history is, because words are much more easily changed when used again and again in speech than when copied in writing. But if there are no written records, such spoken stories are often very helpful. Which of the following is NOT suggested in the passage？ A.Written history is more reliable. B.Written records play an important role in learning about history. C.A written account of our daily activities helps to answer many questions. D.Where there are no written records, there is no history. Little is known about the central Africa 200 years ago because ______.A.there was nothing worth writing down at that time B.people there ignored the importance of keeping a record C.people there did not know how to write D.the written records were perhaps destroyed by a fire “ Remembered history” refers to ______.A.history based on a person’s imagination B.stories of important happenings passed down from mouth to mouth C.songs and dances about the most important events. D.both B and C “ Remembered history” is regarded as valuable only when ______.A.it is written down B.No written account is available C.it proves to be timely D.People are interested in it It is suggested that we could have learned more about our past if ancient people had ______.A.kept a written record of every past event B.burnt their written records in wars C.told exact stories of the most important happenings D.made more songs and dances 请帮忙给出每个问题的正确答案和分析，谢谢！

A．are difficult to detect. B．appear shortly before an earthquake. C．are very destructive. D．appear during an earthquake.

A．A.simple sentence B．B.compound sentence C．C.complex sentence D．D.compound-complex sentence