钟罩阀的作用是什么？

湿地生态系统也叫沼泽，对人类危害很大______．

水是生命之源，它与我们的生活密切相关。在化学实验和科学研究中，水也是一种常用的试剂。

（1）水分子中氧原子核外电子排布图为______________________________；

（2）写出与H₂O分子互为等电子体的微粒______________________（填2种）；

（3）水分子在特定条件下容易得到一个H^＋，形成水合氢离子（H₃O⁺）。下列对上述过程的描述不合理的是___________；

A．氧原子的杂化类型发生了改变

B．微粒的形状发生了改变

C．微粒的化学性质发生了改变

D．微粒中的键角发生了改变（4）在冰晶体中，以一个水分子为中心，画出水分子间最基本的连接方式(水分子用结构式表示)；

（5）下列是钾、碘、金刚石、氯化钠晶体的晶胞图(未按顺序排序)。与冰的晶体类型相同的是_____，D晶体的空间利用率为      。

青春前期的最初标志就是反思能力的出现，这种反思能力是指（）。

A.退回到自我中心的思维

B.主动性的发展

C.对自己心智过程进行思考的能力

D.为了一个共同目标而与他人合作

Selection to participate in a top executive-education program is an important rung on the ladder to top corporate jobs. U. S. corporations (1) billions of dollars in this form of management development -- and use it to (2) and train fast-track managers. Yet one (3) of executive education found that less than 5% of the managers (4) to these high-profile programs are women -- and minorities are terribly (5) as well.

The numbers are (6) . In regular business (7) usually paid for by the participant, not an employer -- there are plenty of women and minorities. Women, for example, (8) for about 30% of MBA candidates. Yet in the (9) programs paid for by corporations that round out a manager’s credentials at a (10) career point, usually at age 40 or 45, companies are making only a (11) investment in developing female and minority executives. A case (12) point: Only about 30% of the 180 executives in Stanford’s recent (13) management program were women.

Most companies say these days they are (14) hiring and promoting women and minorities-- and there are some (15) trends in overall employment and pay levels so why are companies (16) the ball when it (17) executive education The schools (18) that they are neither the cause of nor the cure for the problem. A Harvard Business School dean figures that companies are (19) of sending their female executives (20) they don’t want to lose them to competitors.

17（）

A. comes in

B. comes to

C. comes on

D. comes from

《中华人民共和国特种设备安全法》规定：锅炉、压力容器、压力管道、电梯、起重机械、客运索道、大型游乐设施的安装、改造、重大修理过程，必须经（），未履行该程序，或没达到合格标准，不得交付使用。

A、审批

B、备案

C、监督检验

D、告知