Both, Each, Either; or, and, butParents love their children with

Both, Each, Either; or, and, but
Parents love their children with ______ devotion for ______ they ask for no return.
【正确答案】：a / which
【题目解析】：Mass nouns normally do not take the indefinite article except when they are shifted to the category of countable nouns, in which case they denote type of, kind of.