青春是活力的象征，它蕴含着智慧、勇敢和意志。一个人要保持青春活力最重要的因素是（

窝沟龋的早期表现为（）

A.明显龋洞

B.损害部位透出墨浸状

C.损害部位呈白垩色

D.探诊有酸感

E.损害位于釉牙本质交界处

Access提供两种创建数据库的方法，一种是利用______创建数据库；另一种是先建立一个空数据库，然后再添加数据库对象。

捕碳技术(主要指捕获CO₂)在降低温室气体排放中具有重要的作用。目前NH₃和(NH₄)₂CO₃已经被用作工业捕碳剂，它们与CO₂可发生如下可逆反应：

反应Ⅰ：2NH₃(l)＋H₂O(l)＋CO₂(g)  (NH₄)₂CO₃(aq)ΔH₁

反应Ⅱ：NH₃(l)＋H₂O(l)＋CO₂(g) NH₄HCO₃(aq)ΔH₂

反应Ⅲ：(NH₄)₂CO₃(aq)＋H₂O(l)＋CO₂(g) 2NH₄HCO₃(aq)ΔH₃

请回答下列问题：

（2）为研究温度对(NH₄)₂CO₃捕获CO₂效率的影响，在某温度T₁下，将一定量的(NH₄)₂CO₃溶液置于密闭容器中，并充入一定量的CO₂气体(用氮气作为稀释剂)，在t时刻，测得容器中CO₂气体的浓度。然后分别在温度为T₂、T₃、T₄、T₅下，保持其他初始实验条件不变，重复上述实验，经过相同时间测得CO₂气体浓度，得到趋势图(见图1)。则：

①ΔH₃________0(填“＞”、“＝”或“＜”)。

②在T₁～T₂及T₄～T₅两个温度区间，容器内CO₂气体浓度呈现如图1所示的变化趋势，其原因是____________________________________________________________________________。

③反应Ⅲ在温度为T₁时，溶液pH随时间变化的趋势曲线如图2所示。当时间到达t₁时，将该反应体系温度迅速上升到T₂，并维持该温度。请在该图中画出t₁时刻后溶液的pH变化总趋势曲线。

（3）利用反应Ⅲ捕获CO₂，在(NH₄)₂CO₃初始浓度和体积确定的情况下，提高CO₂吸收量的措施有________________________(写出2个)。

（4）下列物质中也可能作为CO₂捕获剂的是__________。

A．NH₄Cl

B．Na₂CO₃

C．HOCH₂CH₂OH

D．HOCH₂CH₂NH₂

辽阳失守后经略辽东的明朝将领是：（）

A、杨镐

B、熊廷弼

C、袁应泰

D、袁崇焕

American Museum of Natural History is one of the largest natural and historic museums in the world and one of the main natural history research and education centres in the United States, set up in 1869 and located in the west of the Central Park, Manhattan District, New York. It (1) 7 hectares in its total area, (2) classical types of buildings. The (3) of ancient creatures and humanity is (4) the first place of all the museums in the world, (5) the representative samples from South America, Africa, Europe, Asia and Australia were collected, besides those from the (6) country, the United States.

In the museum, there are five kinds of exhibits, including astronomy, mineralogy, human history, and animals in the (7) times and those in modern times. There are thirty-eight exhibition halls with different (8) from 500 to 1,500 square metres. Besides these, there is a Roosevelt Memorial Hall in (9) of President Roosevelt who supported the (10) of the museum, which is also used to have a special exhibition, showing the new important (11) on natural sciences and (12) affairs and social problems, and special topics connected closely with the life of the citizens. Besides this, it is also used for avocation (13) to have all kinds of scientific activities in the laboratories, centres of natural science and centres for citizens. There are more than 10 (14) research departments mainly (15) for collection of samples, research and work of publication.

In the museum, there are (16) and sub-libraries of Aulspond ancient amniote, with about 300 thousand books and magazines (17) natural history, many of (18) are very valuable monographs for the first edition. It has published many expert books and magazines, and a large number of propaganda materials, (19) which are the two magazines, Natural History and Members of Museum that have the biggest (20) of their magazines.

20（）

A.publication

B.symposium

C.circulation

D.tactic