若a=1,|b|=4,则ab的值为( )
±4
一般炮制品的含水量宜控制在()
A.2%~5%
B.7%~13%
C.15%
D.18%~20%
E.25%~30%
走线架的上沿高度应包含布缆高度().
A.250mm
B.200mm
C.150mm
D.100mm