若管道腐蚀程度严重，应尽快降压和维修，则管体腐蚀损伤评定类别为（）。
A.2
B.3
C.4
D.5
参考答案：C
根据句意，用括号内所给单词的适当形式填空。
小题1:Li Hua likes playing football and he plays football _________ (good).
小题2:Koby and Iverson are my __________ (hero).
小题3:Sandy goes __________ (swim) three times a week.
小题4:The watches on the table are those football __________ (play).
小题5:I __________ (real) enjoy the stories he tells me.
如图所示，在倾角为300的粗糙斜面上有一重为G的物体，若用与斜面底边平行的恒力F=G2推它，恰好能使它做匀速直线运动．物体与斜面之间的动摩擦因数为（ ）
A．22
B．33
C．63
D．66
