焊接电缆的长度应根据情况决定,太长则电压降增大,太短则对工作不方便,一般电缆长取()米。
A.10~20
B.20~30
C.30~40
D.40~50
参考答案:B
—________ does he want to be a police officer?
—Because he thinks it interesting to be a police officer. [ ]
A. Why
B. How
C. What
D. Where
汽油机的工作过程中,将内能转化为机械能的是______冲程;将机械能转化内能的是______冲程.