在混合液体中，氮相对于氧和氩来说饱和蒸汽压高，则氮是（）
A、难挥发组分
B、易挥发组分
C、不挥发组分
参考答案：B
—Is that your school ID card?
—_____.[ ]
A. It's my.
B. Yes, it's my.
C. No, it's her.
D. No, it's his school ID card.
物流成本具有哪些特征？简述产品成本与物流成本之间的联系。
