in recent years ,the economic development of the world has been

题目

in recent years ,the economic development of the world has been
In recent years,the economic development of the world has been unbalanced,with Americans ____ more
than they earn.A.spending B.to spend C.spent D.spend
为什么不选b
还有为什么than后面的earn可以用原形?

答案

with的复合结构,后面的spend与Americans之间是主动的关系,是已经进行着,并仍在持续的动作；如果用动词不定式的话,就给人一种还没做或将要去做的感觉.至于后面的earn之所以用原型是因为句中对他并没有时态方面的提示,就用一般现在时就可以了.
:)不知道你明不明白,最好再找老师问一下吧