There was a girl _____ on the playground. [ ]
A. play
B. to play
C. played
D. playing
答案:D
阴阳转化的内在根据有
A.阴阳的对立
B.阴阳的消长
C.阴阳的制约
D.阴阳的互根
E.阴阳的互用
厚壁管在2mm及2mm以下应用套丝连接,对埋入泥土或暗配管宜采用套筒焊接,焊口应焊接牢固、严密,套筒长度为连接管外径的( ),连接管的对口应处在套管的中心。
A.0.5~0.3倍B.0.5~3倍C.1.5~2倍D.1.5~3倍