选择句子，补全对话。
A: Welcome to our school. This is the teacher's office. This is my classroom.
B: 1_____
A: Forty-five.
B: Do you have a library?
A: Yes.
B: Do you have lunch at school?
A: 2_____
A: Look! This is our playground.
B: 3_____
a. Cool! Your school is beautiful.
b. How many students are there in your class?
c. Yes. The canteen is on the first floor.