单项选择题

A.长20cm,内径最细为3~4mm,最粗为7~8mm
B.长25cm,内径最细为3~4mm,最粗为7~8mm
C.长30cm,内径最细为3~4mm,最粗为7~8mm
D.长35cm,内径最细为3~4mm,最粗为7~8mm
E.长40cm,内径最细为3~4mm,最粗为7~8mm