[单选题]对活塞滴定管进行试漏时,先关闭活塞,装入纯水至一定刻线,直立滴定管数分钟,仔细观察液面是否下降,滴定管下端不应有水滴滴下,及活塞隙缝中不应有水渗出，然后将活塞转( 　)等超过2min以上后再观察。
A.90°
B.2７０°
C.３６0°
D.180°

In a recent survey, Garber and Hohz concluded that the average half-hour children’s television show contains 47 violent acts. When asked about the survey network television executive Jean Pater responded. " I sure as heck don’t think that Bugs Bunny’s pouring a glass of milk over a chip-munk’s head is violence. " Unfortunately, both Garber and Holtz and Pater beg the question. The real issue is whether children view such acts as violence.
The violence programming aimed at children almost always appears in the context of fantasy. Cartoon violence generally includes animation, humor, and a remote setting. There is no evidence of direct imitation of television violence by children, though there is evidence that fantasy violence can energize previously learned aggressive response such as a physical attack on another child during play. It is by no means clear, however, that the violence in a portrayal is solely responsible for this ener
A. moral
B. agreeable
C. normal
D. polite

Brighton is a popular seaside town on the south coast of England. Not long ago, some policemen were very (21) . There (22) several serious accidents (23) by motorists driving too fast. The police started to set up a speed trap(速度监视器). They measured (24) of 88 yards on a straight road and watched to see (25) a car took to (26) that far. They knew that if a car took six seconds, it was traveling faster (27) the (28) limit of 30 miles an hour.
When the policemen were ready, they did (29) a hedge(树篱) and started to (30) passing cars. During their first half an hour, they caught five drivers. The policemen wrote down the (31) of each car and the name and address of the (32) . But for the next half an hour the policemen didn’t see anybody (33) too fast. They thought that this was very (34) . One of them drove a quarter of a mile along the road and saw two students (35) A. sign
B. signal
C. number
D. shape