这里in paying比in payment好是因为doing通常暗示主句主语就是动作的主语， the health care company then proved unable to handle the increase in business, falling months behind in paying to doctors and hospitals，pay动作的发起者是 the health care company，用paying ok；
当前面是一个名词，后面需要一个名词与之平行的时候，concrete noun优于gerund。
Ron：
both of them are idiomatically legitimate; they just mean different things.
a plan TO DO X means that people now have the intention of doing X, whereas before they did not.
a plan FOR DOING X means a plan for how to actually execute this action; usually, this construction implies that the intention was already there, but that the plan of execution is new.
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【In contrast to 前后平行-排除ABC】比较对象的不对等。句首的in contrast to要求对比两者必须保证在逻辑上可比。能和“环境学员的方法”相对比的只能是“管理员们的方法”，不能是管理员本身。
D主谓不一致