单项选择题
A.顶部B.左面C.右面D.后方E.下面
A.自上而下,垂直层流B.由内而外,水平层流C.由外而内,水平层流D.自下而上,垂直层流E.自上而下,垂直紊流
A.50mm,50mmB.150mm,150mmC.50mm,150mmD.100mm,50mmE.150mm,50mm