在教学过程中，教学的中心环节是（）。 A.引起学习动机 B.巩固知识 C.领会知识

（10分）硫—碘循环分解水制氢主要涉及下列反应：

Ⅰ. SO₂＋2H₂O＋I₂===H₂SO₄＋2HI

Ⅱ. 2HIH₂＋I₂

Ⅲ. 2H₂SO₄===2SO₂＋O₂＋2H₂O

(1) 分析上述反应，下列判断正确的是         。

a．反应Ⅲ易在常温下进行

b．反应Ⅰ中SO₂氧化性比HI强

c．循环过程中需补充H₂O

d．循环过程产生1 mol O₂的同时产生1 mol H₂

(2) 一定温度下，向1 L密闭容器中加入1 mol HI(g)，发生反应Ⅱ，H₂物质的量随时间的变化如图所示。

① 0～2 min内的平均反应速率v(HI)＝                       。

② 该温度下，H₂(g)＋I₂(g)2HI(g)的平衡常数K＝                 。

③ 相同温度下，若开始加入HI(g)的物质的量是原来的2倍，则           是原来的2倍。

a．平衡常数                 b．HI的平衡浓度

c．达到平衡的时间           d．平衡时H₂的体积分数

(3) 实验室用Zn和稀硫酸制取H₂，反应时若加入少量下列试剂中的       ，产生H₂的速率将增大。

a．NaNO₃         b．CuSO₄           c．Na₂SO₄          d．NaHSO₃

碰碰车大比赛。给下列的问句选择正确的答语。

( ) 1. What do you do in winter?      ( ) 2. What are you doing?            ( ) 3. Why do you go to the library?  ( ) 4. How many months in a year?     ( ) 5. Where can you play basketball? a. Twelve.                       b. I am doing my homework.        c. At the gym.                                                                   d. I make a snowman.              e. Because I want to read books.

诊断急性胰腺炎最有意义的指标值（）。

A.血钠

B.血肌酐

C.血淀粉酶

D.尿淀粉酶

E.血心肌酶

房地产经纪执业规范的落实和执行主要依靠的是：( )。

A．行业的自律

B．企业的自律

C．交易人员自觉

D．执业人员自觉

E．产业的自律

A Trip to the Forest

One day Bob took two of his friends into the mountains. They put up their tents and then rode off to a forest to see how the trees were growing.
In the afternoon when they were about ten kilometres from their camp, it started to snow. More and more snow fell. Soon Bob could hardly see his hands before his face. He could not find the road. Bob knew there were two roads. One road went to the camp, and the other went to his house. But all was white snow. Everything was the same. How could he take his friends back to the camp
Bob had an idea. The horses ! Let the horses take them back ! But what would happen if the horses took the road to his house That would be a trip of thirty-five kilometres in such cold weather!
It was getting late. They rode on and on. At last the horses stopped. Where were they None of them could tell. John looked around. What was that under the tree It was one of their tents!

John and his two friends went to the forest to ______.

A．build their camp

B．find their way home

C．enjoy the mountains in the snow

D．watch the trees in the forest