泵抽空时压力、电流大幅波动或无指示。

X、Y、Z、Q四种元素的核电荷数分别为a、b、c、d，若它们的离子X^m+、Yⁿ⁺、Z^m-、Q^n-的电子层数相同．下列关系正确的是（　　）

A．a-b=n-m

B．b-d=2n

C．c-d=m+n

D．a-c=0

服从指在他人命令或要求下所实现的自己本来不愿做的行为，亦即按他人旨意行事。 下列属于服从的是( )。

A．小杨很想去北京，可一直未有机会。一天公司老总对小杨说：“明天你出差去北京。”小杨说：“一切听老总安排。”第二天小杨就去了北京

B．小侯正在打篮球，突然听到组长小王在大声对他说：“小侯，你的作业还未做呢!你现在就得去做。”小侯听后，勉强地抛下球，向教室奔去

C．小丁周五下午放学后陪同学小李到超市玩了近两个小时

D．小于的妻子小陈刚怀孕，小陈对小于说：“从今日起，不准你在家抽烟。”小于愉快地答应了，但不一会儿就在家里抽起了烟

儿童自我意识与自我教育能力的发展大致经历如下过程( )

A．从自我为中心发展到“他律”再到“自律”

B．从“他律”发展到“自律”再到自我为中心

C．从自我为中心发展到“自律”再到“他律”

D．从“自律”发展到“他律”再到自我为中心

针对当时建筑施工中工伤事故频发的严峻形势，国家有关部门颁布了《建筑业安全生产实施细则》。但是，在《细则》颁布实施两年间，覆盖全国的统计显示，在建筑施工中伤亡职工的数量每年仍有增加。这说明，《细则》并没有得到有效的实施。 以下哪项如果为真，最能削弱上述论证( )

A．在《细则》颁布后的两年中，施工中的建筑项目的数量有了大的增长

B．严格实施《细则》，将不可避免地提高建筑业的生产成本

C．在题干所提及的统计结果中，在事故中死亡职工的数量较《细则》颁布前有所下降

D．在《细则》颁布后的两年中，在建筑业施工的职工数量有了很大的增长

There is virtually no limit to how one can serve community interests, from spending a few hours a week with some charitable organization to practically full-time work for a social agency. Just as there are opportunities for voluntary service (1) (VSO) for young people before they take up full-time employment, (2) there are opportunities for overseas service for (3) technicians in developing countries. Some people, (4) those who retire early, (5) their technical and business skills in countries (6) there is a special need.

So in considering voluntary or (7) community service, there are more opportunities than there (8) were when one first began work. Most voluntary organizations have only a small full-time

(9) and depend very much on volunteers and part-timers. This means that working relationships are different from those in commercial organizations, and values may be different. (10) some ways they may seem more casual and less efficient, but one should not (11) them by commercial criteria. The people who work with them do so for different reasons and with different (12) , both personal and (13) . One should not join them (14) to arm them with professional experience; they must be joined with commitment to the (15) , not business efficiency. Because salaries are (16) or non-existent many voluntary bodies offer modest expense. But many retired people take part in community service for (17) , simply because they enjoy the work.

Many community activities possible (18) retirement were also possible during one’s working life but they are to be undertaken (19) seriously for that. Retired people who are just looking for something different or unusual to do should not consider (20) community service.

18（）

A.before

B.on

C.in

D.at