用碘化钾碱性高锰酸钾法测定高氯废水中的化学需氧量时，若水样中含有几种还原性物质，则取它们的平均K值作为水样的K值。
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胶质的H／C原子比同沥青质相比是（）。
A. 高
B. 低
C. 稍低
D. 相等
Which statement concerning the navigation of a vessel in ice is FALSE?（）
Anchoring in the presence of ice is not recommended except in an emergency
B. Towing a vessel through an ice field is not recommended except in an emergency
C. The "Free and Proceed" system of escorting a beset vessel cuts down on the number of freeing operations
D. When anchoring in ice，it is advisable to increase the scope of the chain over what is normally used for non-icing conditio
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