机械加压送风系统采用内表面光滑的混凝土等非金属材料风道时,其风速不应大于( )。
A.10m/s B.15m/sC.20m/s D.25m/s
参考答案:B
Doctors should take special care when treating children because their breathing rate is different from _____ of adults.
A.one
B.those
C.that
D.some
铅酸蓄电池放电时,阴阳极板表面都会逐渐形成()薄层。