Sufficient cargo tanks shall be（）prior to each ballast voyage in order that，taking into account the tanker’s trading pattern and expected weather conditions，ballast water is put only into cargo tanks which have been crude oil washed.

A.inerted

B.crude oil washed

C.gas freed

D.batterned down

计算题：根据下列水质的分析结果：

〔Ca^2＋〕＝54.0mg∕L，〔HCO₃^－〕＝170.8mg∕L，〔Mg^2＋〕＝9.6mg∕L，〔SO₄^2－〕＝43.2mg∕L，

〔Na^＋〕＝11.5mg∕L，〔Cl^－〕＝10.65mg∕L。

试求①阴、阳离子组合成各种假想化合物的组成和浓度；②水样中各类硬度的数值。