A. How much are they?

B. Can I help you?   

C. OK. We'll take them.

D. What size ?

E. Yes. But I like the blue pair.

A:____

B: Yes. A pair of shoes for my son.

A:____

B: Size6.

A: How about this pair?

B: Are they nice，John?

C:____

B: Are the blue ones all right?

C: Yes. they are.

B:____

A: They are 40 yuan.

B:____

下列指定反应的化学方程式正确的是（　　）

My students，________you have a heart loving life，you always can find things that would make you happy each day.

①若a，b，c∈R，则“ac²＞bc²”是“a＞b”成立的充分不必要条件；②命题“∃x₀∈R， $x_0^2$ ＋x₀＋1＜0”的否定是“∀x∈R，x²＋x＋1≥0”；③命题“若|x|≥2，则x≥2或x≤－2”的否命题是“若|x|＜2，则－2＜x＜2”；④函数f(x)＝ln x＋x－ $\frac{3}{2}$ 在区间(1,2)上有且仅有一个零点．