A cloud sequence of cirrus，cirrostratus，and altostratus clouds followed by rain usually signifies the approach of a(n)（）.

A . provide the proper trim B . prevent negative stability from developing C . prevent excessive longitudinal stresses D . control list

A . it will be preceded by a sudden increase in wind speed B . it will be preceded by a sudden decrease in wind speed C . the wind speed will not change as it passes D . the wind will back rapidly to left in a counterclockwise direction as it passe

A . A sequence will never generate duplicate values B . The MAXVALUE of a sequence can be equal to the MINVALUE C . It is not possible to create a sequence that generates a constant since the INCREMENT value must be greater than zero D . When a sequence cycles back to either the MAXVALUE or MINVALUE, it will always be equal to the specified value of either of these two boundarie

A . darkening，growing in size and forming an anvil top B . that shows extensive vertical development C . creating cold downdrafts that are felt on the ground D . All of the above

A . Cirrostratus B . Cirrus C . Cirrocmulus D . Altostratu

A . Shut down the database. B . Set the appropriate parameters in init.ora file. C . Start the database in NOMOUNT state. D . Issue the ALTER DATABASE ARCHIVELOG command. E . Open the database. F . Take a full closed backup.

A . warm front B . occluded front C . medium front D . cold front

A . CONTROL B . UPDATE C . USAGE D . ALTER

A . cirrus B . cirrocumulus C . altocumulus D . cumulonimbu

A . break glass，pull valve，break glass，pull cylinder control B . sound evacuation alarm，pull handle C . open bypass valve，break glass，pull handle D . open stop valve，open control valve，trip alarm

A . cold front B . warm front C . tropical front D . occluded front

A . bar of the storm B . eye of the storm C . funnel D . front

A . heavy rain B . heavy snow C . thick fog D . clearing skie

A . Nimbostratus B . Altostratus C . Cumulonimbus D . Cirru

A . occluded front B . warm front C . cold front D . warm sector

A . ice crystals B . water droplets C . snow crystals D . nitroge

识别SD序列(Shine—Dalgarno sequences)的是()。 A．5'-end of 18S rRNA B．5'-end of 16S rRNA C．3'-end of 18S rRNA D．3'-end of 16S rRNA

Pre-sequences are a fundamental unit of conversational structure.()

What is the definition of a path？ () A．A sequence of vertices and the edges formed by each successive pair of vertices B．A walk with distinct vertices C．A walk with distinct edges D．None of the above

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、A happens first B、B happens first C、A and B happen at approximately the same time D、Not given

A．real B． fixed C． actual D． virtualized