还有几个英语问题Most of students don't know __so much homework e

还有几个英语问题
Most of students don't know __so much homework every work every day.

为什么填what to do with 而不填 how to do with
in winter ,people usually keep flowers in their houses to protect them aganist the cold weather.
求翻译
pain 表示疼痛时好像大部分不可数,但也有可数的情况.能否说明一下


马上就要考试了,这几个问题查了好久也没有满意的回答.