试解释为何着火和点火存在着火浓度界限？

--- Do remember to take this medicine three times a day with warm boiled water.

---________.

A．Heard it

B．Got it

C．Take it

D．Make it

以下反应均在密闭容器中进行，根据相应的图象，下列相关说法正确的是（　　）

A．图1所示为t₀时改变某一条件时速率变化，则改变的条件一定是加入催化剂

B．图2所示为反应达到平衡时温度对化学平衡的影响，则正反应为放热反应

C．图3所示为反应达到平衡时压强对化学平衡的影响，则反应方程式中a＜b

D．图4所示为平衡后加压时反应速率的变化，则A、B是气体、D为固体或液体

阅读下面一段文字，完成下列4题。

①生物体都具有感觉器官，无论是感知物理信息抑或检测化学信息的这些自然感测器，都是生物体藉以获得生存必需信息的良好帮手。然而人要获得客观世界的大量信息，光凭人类自身的感觉器官是远远满足不了的，必须借助人造的各类感测器。

②科学家们首先想到的是存在于生物体内的2000多种不同的酶。由于在人体生命活动中担任催化剂作用的酶具有严密的对象选择性，即某一种酶只促成对应的某种对象的化学反应，科学家们就巧妙地设计出各种带不同酶的生物类化学感测器。为了克服酶会溶于水而不能反复使用的技术难题，他们又将酶涂布在高分子膜上，然后将这种带酶的膜放进所测试的采样中，催化受质(待测的特定化学物质)的化学反应。在膜附近产生或消耗的其他化学物质，通过膜上带有的碳电极测定化学物质的浓度变化，就能间接地计算出原受质的浓度。这样，只要使用不同的酶，便可制成测定各种不同化学物质的生物感测器了。

③这种生物感测器是高技术的结晶。它利用了先进的印刷和半导体加工技术。先在基板上印刷碳电极，再印刷附着特定酶的膜，之后裹上多孔的高分子膜，类似集成电路的制作。一般是在同一基片上制成大量感测元件，只要将它们切开，就能同时制成多枚生物感测器。

④如今科学家已不满足于上述利用物质电特性制成的生物感测器，他们又投入以物质的光特性为基础的光纤传感类的新型生物感测器的研制，并将其广泛应用于各个领域。

从列出的概念中选择五个，分别填在图示的处，使其正确揭示人造感测器的研制程序（）。

①克服酶会溶于水而不能反复使用的技术难题

②将酶涂布在高分子膜上

③将带酶的膜催化受质的化学反应

④测定化学物质的浓度变化

⑤计算出原受质的浓度

⑥在基板上印刷碳电极

⑦印刷附着特定酶的膜

⑧裹上多孔的高分子膜

⑨切开同一基片上大量感测元件

A．①⑥⑦⑧⑨

B．①②⑥⑦⑧

C．②⑥⑦⑧⑨

D．①⑥⑦⑧⑨

B

It is surprising that eating three meals a day ─ breakfast, lunch, and dinner ─ has been a custom only since 1890. Before this time, they only had two meals a day ─ breakfast and dinner.

In the 16th century, breakfast was only to break one's fast (随便吃一点). But 200 years later it had become a large meal , not just for family, but for numbers of guests as well. It was a social event, It began at 10 a.m. and lasted until l p.m.. Then breakfast began to be less popular. It became , instead, a lighter meal and was taken at a much earlier hour. By 1850 it had been pushed hack to 8 a.m.. and became a family meal.

Dinner, however, went the other way. In the 16th century it was eaten at 11 a.m.. Years later, it had moved to the early afternoon, then to 5 p. m.. By 1850 dinner time had reached 7 p.m. Lunch is a recent idea. It first appeared as a snack to fill the gap between breakfast and dinner.

59. English people did not have lunch _________.

A. before 1890    B. after 1890        C. after 16th century   D. by 1850

60. "Dinner, however, went the other way" means _________.

A. Dinner didn't go there with breakfast    B. Dinner took the same way with breakfast

C. Dinner is different from breakfast        D. Dinner is the same with breakfast

61. Lunch has been served since the end of the ________ century.

A. seventeenth    B. eighteenth        C. sixteenth           D. nineteenth

62. The selection is mostly concerned with _________.

A. what people eat for breakfast         B. what people eat for dinner

C. the history of supper                D. the history of breakfast

63. The selection leads the reader to believe that __________.

A. our custom of meals is based on English custom

B. before 1890 people also ate three meals a day

C. breakfast is the most important meal for us

D. the body can adjust to two or three meals a day      

公文发文的规范，必须考虑和遵守公文的（）。

A.行文制度

B.行文原则

C.选材标准

D.文章立意

E.构思方式