煤气设备均必须保持正压操作,在设备停止生产而保压又有困难时,则应可靠地(),并将内部煤气吹净。
A、放散
B、切断煤气来源
C、关闭
参考答案:B
Drug use is rising dramatically among the nation’s youth after a decade of decline. From 1993 to 1994, marijuana use among young people (1) from 12 to 17 jumped 50 percent. One in five high school seniors (2) marijuana daily. Monitoring the Future, which (3) student drug use annually, reports that negative attitudes about drugs have declined for the fourth year in a row. (4) young people see great risk in using drugs. Mood-altering pharmaceutical drugs are (5) new popularity among young people. Ritalin, (6) as a diet pill in the 1970s and now used to (7) hyperactive children, has become a (8) drug on college campuses. A central nervous system (9) , Ritalin can cause strokes, hypertension, and seizures. Rohypnol, produced in Europe as a (10) tranquilizer, lowers inhibitions and suppresses short-term memory, which has led to some women being raped by men they are going out with. (11) taken with alcohol, its effects are greatly (12) . Rock singer Kurt Cobain collapsed from an (13) of Rohypnol and champagne a month before he committed (14) in 1994. In Florida and Texas, Rohypnol has become widely abused among teens, who see the drug as a less expensive (15) for marijuana and LSD. Alcohol and tobacco use is increasing among teenagers, (16) younger adolescents. Each year, more than one million teens become regular smokers, (17) they cannot legally purchase tobacco. By 12th grade, one in three students smokes. In 1995, one in five 14-year-olds reported smoking regularly, a 33 percent jump (18) 1991. Drinking among 14-year-olds climbed 50 percent from 1992 to 1994, and all teens reported substantial increases in (19) drinking. In 1995, one in five 10th graders reported having been drunk in the past 30 days. Two-thirds of high school seniors say they know a (20) with a drinking problem.
2()
A.tastes
B.smokes
C.injects
D.takes
下列关于钢尺普通量距的说法,正确的有()
A.钢尺普通量距精度要求应达到1/3000
B.钢尺普通量距时应将钢尺拉紧、拉平、拉稳
C.钢尺普通量距时,钢尺弯曲总是使量距结果大于实际距离
D.倾斜地面钢尺普通量距可采用平量法或斜量法
E.普通钢尺量距时进行直线定线,必须采用经纬仪定线