选项

物质（括号内为杂质）

选用试剂

A

C（Fe）

盐酸

B

CaCl₂溶液（HCl）

Ba（OH）₂溶液

C

CO₂（CO）

碱石灰（CaO和NaOH的混合物）

D

NaOH溶液Ca（OH）₂

K₂CO₃溶液

No. 1 Middle School

Don't run in the hallways

Don't bring food into the classroom.

Don't listen to music in class.

You have to wear a uniform.

No. 2 Middle School

Don't bring food into the classroom

Don't wear a hat in class.

You have to wear a uniform.

Don't go into the classroom without the teacher.

No. 3 Middle School

Don't listen to music in the classroom.

Don't run in the hallways.

Don't go into the classroom without the teacher.

You have to wear sports shoes for gym class.