as to = concerning, about 相等于介词,原句的正常语序为：the question as to who should go out this morning to clean the snow arises.为了避免头重脚轻,把谓语arises提前 ,把as to.这个介词短语（作定语）就放...那who 能写成whom 吗？不行啊，who在从句里作主语用，只能用主格。whom 是做宾语用的 who should go out this morning to clean the snow 是介词as to 的宾语从句，who 是引导词，在从句里做主语。