简述准时采购与传统采购的区别。
If,during helicopter refueling operations,fuel is spilled on clothing,the person should first（）. ["see the medic immediately","spray hinself with foam or CO","complete his task and then see medic","remove the clothing and wash"]
下面不属于科研选题评价必须遵循的标准的是（）。 ["事实标准","转化标准","需要标准","逻辑标准"]
在科学研究中，人们通过对科学背景知识的认真思索和分析，从中发现各种矛盾，它是现有人类认识未解决的矛盾，这种矛盾或疑难，就是（）。 ["简单问题","科学问题","一般问题","复杂问题"]
主要由外力沉积作用造成的是（） ["珠江三角洲","长江三峡","桂林山水","黄土高原的千山万壑"]
简述国际航运系统的组成。
