图书分类法中,类名之间的上下位关系反映了学科概念之间的( )关系。
Goods are carried by several of transport--on road or rail, by sea or air.
You can _____ some bottles of wine, or some chocolates, or a bunch of flowers.
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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