用山、石、花等将园林中一些不足或丑陋之处加以掩盖或处理，使之变成一种美景的方法叫（）

某活动课程小组拟用50mLNaOH溶液吸收CO₂气体，制备Na₂CO₃溶液．为了防止通入的CO₂气体过量生成NaHCO₃，设计了如下实验步骤：

a．取25mL NaOH溶液吸收过量的CO₂气体，至CO₂气体不再溶解；

b．小火煮沸溶液1～2min；

c．在得到的溶液中加入另一半（25mL）NaOH溶液，使其充分混合反应．

（1）此方案能制得较纯净的Na₂CO₃，写出a、c两步的化学反应方程式______、______．

此方案第一步的实验装置如图所示：

（2）加入反应物前，如何检查整个装置的气密性？______（3）装置B中盛放的试剂是______，作用是______．

（4）在实验室通常制法中，装置A还可作为下列______气体的发生装置（填序号）．

①CH₂═CH₂    ②H₂S    ③CH₄    ④CH≡CH     ⑤H₂

（5）实验室制取下列气体：①NH₃，②Cl₂，③HCl，④H₂S，⑤CH₄，⑥CO，⑦CO₂，⑧O₂时，属于必须进行尾气处理，并能用下图所示装置进行处理的，将气体的序号填入装置图的下方空格内．

（6）已知所用NaOH溶液中溶质的质量分数为40%，室温下该溶  液密度为1.44g/mL，假设反应前后溶液的体积不变，不考虑实验误差，计算用此种方法制备所得Na₂CO₃溶液的物质的量浓度为______．

做结核菌素试验后多长时间看结果（）

A.24～36小时

B.48～72小时

C.3～4周

D.5～8周

E.20分钟

患者缺失3个月，要求固定修复。

决定其能否固定桥修复的因素，除了（）

A．邻牙牙周支持能力

B．邻牙牙冠大小、形态

C．缺牙区粘膜厚度

D．咬合关系

E．邻牙的位置

对于不记名证券而言，完成了清算和交收，还要完成登记过户，证券交易过程才告结束。( )

When you stop and think about your high school or college alma mater, were your experiences more positive or negative Do your feelings of (1) in that school have anything to do with whether or not your school was single-sex or coed (2) to send their children to single-sex schools, because they feel both (3) when they study in the company of students of the same sex. They (4) .
For years, only parents who could afford to send their children to private schools, or who had (5) , chose single-sex education for their children. Single-sex schooling was (6) for most American families. Today, however, along with (7) , public schools are experimenting with the idea of (8) .
Girls may be the ones who benefit most from single-sex schooling. Studies have shown that (9) in coed classrooms because teachers sometimes pay more attention to boys. Girls’ (10) toward their studies tends to disappear as they begin to feel less successful. They start to (11) outperform them in math and science. As boys (12) , girls start to lose it. Moreover, adolescence is (13) for girls. As they experience adolescent changes, some girls become depressed, develop an addiction, or suffer from (14) .
In the early 1990s, some influential people said that being in single-sex classes could (15) . Schools across the country began creating single-sex classrooms and schools. But many critics claim that (16) may actually be detrimental to a girl’s education because they (17) of sex differences.
The renewed interest in single-sex schooling (18) among Americans. Those who give it full endorsement believe girls need an all-female environment to take risks and find their own voices. Those who (19) of single-sex schooling wonder whether students’ lack of achievement warrants returning to an educational system that divides the sexes. They believe there is no (20) .