甲：v（X）=0.3mol•L^﹣1•min^﹣1，乙：v（Y）=1.2mol•L^﹣1•min^﹣1，

丙：v（Z）=0.8mol•L^﹣1•min^﹣1，丁：v（W）=0.02mol•L^﹣1•s^﹣1，则反应最快的是（   ）

在课外实践活动中，用闪光照相机探究纸锥竖直下落的运动情况，照相机每隔0.2s曝光一次。

请回答下列问题：

（1）﹣定温度下，向0.1mol/LCH₃COOH溶液中加入少量CH₃COONa晶体时，下列说法正确的是____ ．（填代号）

a．溶液的pH减小 b．CH₃COOH的电离程度减小

c．溶液的导电能力增强  d．溶液中c（OH^﹣）•c（H⁺）不变

（2 ）25°C 时，0.10mol/L Na₂CO₃ 溶液的 pH=11，则溶液中由水电离出的 c（OH^﹣）=____ mol/L．

（3）己知快K_sp只与温度有关，溶解平衡：CaCO₃（s）⇌Ca²⁺+（aq）+A^2﹣（aq）△H＞0．

①温度升高时，K_sp____．（填“增大”“减小”或“不变”，下同）

②向浊液中通入HCl气体c（ Ca²⁺）____ 

（4）己知醋酸的电离常数k=1.8×l0⁵．25°C时，向CH₃COOH溶液中加入一定量的NaHCO₃，所得混合液的 pH=6，则混合液中 c（CH₃COO^﹣）/c（CH₃COOH）=____ ．

A: Hi, Michael! You look worried. Anything wrong?

B: It's Kangkang. ____ I really worried about him.

A: I'm sorry to hear that. He must feel bored and lonely. ____

B: We can bring him some exciting CDs and DVDs. And we can come over to see him. (At Kangkang's home)

C: I am very happy that you come to see me. You know I missed lots of lessons and I am really worried about that.

B: ____

C: ____ How about the football match?

A: Don't worry. ____ 
C：That's very nice of you.