题干
— It's clever _____ you to help me work out this difficult maths problem. Thanks.
— You are welcome. Now it's easier _____ you to understand it.
A：of; of
B：of; for
C：for; of
D：for; for
答案(点此获取答案解析）
B
成了白色沉淀，将白色沉淀加入稀硫酸中，又生成了红色粉末状固体和SO2，同时溶液呈蓝色。根据实验现象分析推测，下列描述正确的有