The buses, ________ were already full, were surrounded by an angry crowd.

A．most of them

B．which most

C．most of which

D．that most

江西省的天沐温泉远近闻名．经分析鉴定，天沐温泉的水中含有较多的硫酸根离子，以及钾、钙、钠、锌、锶等多种对人体有益的微量元素．欲鉴定温泉水中含有硫酸根离子，应采取的方法是（　　）

A．滴加硝酸

B．滴加KOH溶液后，再加盐酸

C．滴加Ba（NO₃）₂后，再加稀硝酸

D．滴加K₂CO₃后，再加稀硝酸