十字头是活塞式压缩机的() A.运动机构 B.工作机构 C.机身 D.调节系统

题型:单项选择题

问题:

十字头是活塞式压缩机的()

A.运动机构

B.工作机构

C.机身

D.调节系统

考点:压缩机工考试初级压缩机工初级压缩机工题库
题型:单项选择题

设a、b、c表示三条直线,α、β表示两个平面,则下列命题的逆命题不成立的是(  )

A.c⊥α,若c⊥β,则αβ

B.b⊂β,c是a在β内的射影,若b⊥c,则a⊥b

C.b⊂β,若b⊥α则β⊥α

D.b⊂α,c⊄α,若cα,则bc

题型:单项选择题

X、Y、Z为短周期元素,形成的简单离子为Xn+、Ym+、Zn-,已知带有电荷的数值m>n,且X、Y、Z三种原子的M电子层中的电子数均为奇数.若按X、Y、Z为顺序的下列说法中,正确的是(  )

A.原子半径依次增大

B.常温常压下单质的密度依次减少

C.它们的最高价氧化物对应水化物两两之间均能反应

D.X单质能将Y从其盐的水溶液中置换出来

题型:单项选择题

葫芦素XG可以作为()的替代品。

A.盐

B.防腐剂

C.辣椒

D.糖

题型:单项选择题

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.

12()

A.enlarged

B.confirmed

C.exaggerated

D.magnified

题型:单项选择题

中国的武术主要有哪些内容?

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