单项选择题
A.5~10mm B.6~12mm C.7~14mm
A.10m/s B.12m/s C.14m/s
A.0.1~0.2Mpa B.0.2~0.3Mpa C.0.3~0.4Mpa
A.1/2 B.2/3 C.3/4
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