带加热衬套的螺杆泵，适用于高粘、流动性差的液体输送。加热介质一般采用（）。
A.电流
B.蒸汽
C.烟气
D.热水
参考答案：B
— What do you think of the little girl's singing on the Walk of Fame, a program on CCTV?
— _____and everybody present was____. [ ]
A. Impressing; impressed
B. Impressed; impressive
C. Impressive; impressed
D. Impressive; impressing
什么是燃料的发热值？
