北宋时，出产的瓷器质地细腻，色泽莹润，后来发展为瓷都的是（    ）

已知某固体混合物A中含有CuSO₄、FeCl₃、NaNO₃、BaCl₂、CaCO₃，五种物质中的两种或多种按下述步骤进行实验探究，观察实粒现象，并加以分析推理（设过程中所有发生的反应都恰好完全反应）

Ⅰ．取一定质量的该固体混合物A放入一洁净烧杯中，向其中加入适量NaOH溶液、搅拌，待烧杯中物质充分反应后，过滤，得到褐色沉淀B和滤液C

Ⅱ．另取一定质量的该固体混合物A放入另一结晶烧杯中，向其中加入适量H₂SO₄溶液、搅拌，待烧杯中物质充分反应后，过滤，得到白色沉淀D和滤液E

Ⅲ．将所得溶液C和溶液E充分混合，再向混合后的溶液中加入适量AgNO₃溶液，待充分反应后，过滤，得白色沉淀F和滤液G

Ⅳ．根据上述实验过程和发生的现象做出相应的推理，填写以下空白：

   Bob was cutting a branch（树枝） off a tree in his garden. While he was sawing（锯）, another man passed in the street. He stopped and said, “ Excuse me, but if you continue (继续)to saw（锯） that branch like that, you will fall down with it.” He said this because Bob was sitting on the branch and cutting it at a place between himself and the trunk（树干） of the tree.
   Bob said nothing. He thought, “ This is some foolish（愚笨的） person who has no work to do and goes about telling other people what to do and what not to do.”
   The man continued on his way. Of course, after a few minutes. The branch fell and Bob fell with it.
   “My God!” he cried. “That man knows the future!” and he ran after him to ask how long he was going to live. But the man had gone.