One day，a little boy came to a shop and said to the shop assistant(店员): "I want to buy twelve exercise-books of 10 cents(美分)(100美分=1美元) and nine pencils of 15 cents, four erasers of 20 cents. How much shall I pay(付款)?"
The shop assistant wrote all numbers down on a piece of paper and calculated(计算). Then she said, “You should pay 3.35 dollars altogether(合计).”
"If I give you 5 dollars, how much shall I get back?"
"You'll get back 1.65 dollars. Shall I pack(打包) these things for you?"
"No, I don't buy anything" the boy looked at the piece of paper and said politely(礼貌地). "This is my math homework. Can I take the answer away?"
_______ kinds of things are mentioned by(被提到) the boy.

A．One

B．Two

C．Three

D．Four

The boy went to the shop _______.

A．to buy something for his school

B．to buy something for his home

C．to see how many things the shop has

D．to get an answer

The shop assistant asked(要求) the boy to pay _____ after she answered the boy.

A．nothing

B．$ 3.35

C．$ 1.65

D．$ 5

The boy bought(买) ________ at last(最后).

A．nothing	B．nine pencils
C．twelve exercise-books	D．four erasers