简述掘进巷道水幕安设的要求。

两样本均数差别的假设检验用t检验的条件是（）

A.两总体均数相等

B.两总体方差相等

C.两样本均为大样本

D.两样本均为小样本

E.两总体均符合正态分布

高速磨削时的砂轮圆周线速度可达到______以上。

A．35m/s

B．50m/s

C．70m/s

阅读理解。

     A million motorists leave their cars filled up with petrol and with the keys in the ignition (点燃) every day.

The cars are sitting in petrol stations while drivers pay for their fuel. The Automobile Association(A.A) has

discovered that cars are left unattended for an average three minutes and sometimes longer as drivers buy

drinks, sweets, cigarettes and other consumer items.With payment of credit cards becoming more and more

common, it is not unusual for a driver to be out of his car for as long as six minutes, providing the car theft

with a golden opportunity.

     For more than ten years there has been a big rise in car crime than in most other types of crime. An average

of more than two cars a minute are broken into or stolen in the UK. Car crime accounts for almost a third of

all reported offenses with no signs that the trend is slowing down.

     Although there are highly professional criminal involved in car theft, almost 90 percent of car theft is

committed by the opportunists. Amateur thieves are aided by our own carelessness. The A.A. recommends

locking up whenever you leave the car and for however short a period. A partially open sunroof or window is

a further come-on (诱惑) to thieves.

     There are many other traps to avoid. The A.A. has fond little awareness among drivers about safe parking.

Most motorists questioned made no efforts to avoid parking in quiet spots-just the places thieves love. The A.A.

advises drives to park in places with people around because thieves don't like audiences.

1. We can learn from the passage that _____.

A. there is an increasingly large number of car crimes in the UK

B. about 20% of all reported crimes involve cars

C. car crime is decreasing gradually

D. the A. A. didn't pay much attention to car crimes

2. The underlined word "opportunists" in this passage most probably refers to _____.

A. people who take chances to steal into cars

B. people who always steal or break into cars

C. highly skillful criminals

D. careless criminals who tend to fail in their crimes

3. The A. A, suggests that the car owners should _____.

A. always lock up their cars when they leave

B. keep the sunroof and windows open

C. avoid parking in crowded places

D. keep some people around to watch their cars

4. Paragraph Three mainly talks about _____.

A. the professional car criminals

B. the opportunities for non-professional car thieves

C. the anti-theft tips

D. when to lock the car

企业收到投资方以现金投入的资本，实际投入的金额在注册资本中所占份额的部分，应记入（）科目。

A、实收资本

B、资本公积

C、盈余公积

D、利润分配

门静脉高压分流术的主要目的是（）。

A.制止出血

B.消除腹水

C.消除脾亢

D.根除肝损害

E.纠正肝性脑病