题干
— that made him unhappy?
—Well, failing in his English test.
—Well, failing in his English test.
A：Where was it
B：What was it
C：How was it
D：Why was it
答案(点此获取答案解析）
B
溶液至过量，同时加热，沉淀的物质的量先增多后减少，但最终仍有沉淀未溶解，在此过程中还有刺激性气味气体生成。