— Were there any cows?
— ________.
A：Yes, there were
B：No, there aren't
C：Yes, there are
D：No, there were
有100mL 溶质为MgCl2和AlCl3的混合溶液，c（Cl﹣）=1.0mol•L﹣1，c（Mg2+）=0.2mol•L﹣1．若不考虑水解因素，则要使其中的Mg2+全部转化为Mg（OH）2沉淀而分离出来，至少需要4mol•L﹣1的NaOH溶液的体积是（ ）
在一定质量的某Na2SO4溶液中加入足量的BaCl2溶液，所得沉淀质量等于原Na2SO4溶液质量的12，则原Na2SO4溶液中溶质的质量分数接近于（ ）
