With more forests being destroyed, huge quantities of good earth ________ each year．
A.is washing awayB.is being washed awayC.are washing awayD.are being washed away在线课程D
解析：
此题考查了两个知识点。其一是主谓一致：根据quantity的用法，quantities of和a quantity of后面都可加不可数名词与可数名词复数，但它们作主语时，quantities of...后面的谓语动词用复数，而a quantity of...的谓语动词用单数，故排除A、D项；
其一考查了语态，土壤是被冲走的，这里应该用被动语态，正确答案是D项。