读短文，完成下面的选择题。

Dear John,

      Please come to my eleventh birthday party at 6 p.m. on Saturday. Now let me tell you how to come:

      1. Start from the bus stop near your home.

      2. Take the No.21 bus.

      3. Get off at the science museum.

      4. Walk south for three minutes.

      5. My home is next to the white building.

      6. Look for me near the door.

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Yours,

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Zhang Peng

1. John is one year younger than Zhang Peng. How old is John?

A. 10

B. 11

C. 12

2. Which bus should John take?

A. No.7 bus.

B. No.14 bus.

C. No.21 bus.

3. Where should John get off?

A. At the hospital.

B. At the school.

C. At the science museum.

4. Zhang Peng's home is _____________ a white building.

A. north of

B. next to

C. south of

普通碳素钢和优质碳素钢的区别在于含碳量不同。