单项选择题
A.60kPa B.100kPa C.140kPa D.180kPa
A.30kPa B.40kPa C.50kPz .D.60kPa
A.1条竟为50mm B.1条宽为100mm C.2条宽为50mm D.2条宽为100mm
A.4个 B.6个 C.7个 D.8个
微信扫一扫,加关注免费搜题