状态参数沿闭合路径的积分

ph 4, why does theuthor mention the outline The outline is employed to group musicins into right ctegories. B．The outline is hypothesis formed by the reserchers in this field. C．The outline helps to distinguish importnt musicins from unimportnt musicins of ech er. D．This outline helps to unify the musicins of the sme period regrding their style.A．The outline is employed to group musicians into right categories．B．The outline is a hypothesis formed by the researchers in this fielDC．The outline helps to distinguish important musicians from unimportant musicians of each erAD．This outline helps to unify the musicians of the same period regarding their stylE．

A、货物的运输条件因素
B、货源因素
C、运费因素
D、运输途中风险因素