单项选择题
A.2τ B.4τ C.8τ D.16τ
A.12.kN·m,-3kN·m B.-2.5kN·m,-3kN·m C.-2.5kN·m,-3kN·m D.2.5kN·m,-3kN·m
A.3.5mm B.1.8mm C.2.7mm D.1.4mm