在多个采暖建筑物的同一供热系统中，应当安置（）个膨胀水箱。
A.3
B.2
C.1
D.多个
参考答案：C
（3x4）2+（x2）4=______．
— We are going to have a barbecue in Nanshan Park tomorrow.
— _____[ ]
A. Have a good time!
B. Congratulations!
C. Hurt's true!
D. That's nothing!
