Children often _____solution to the problem required many hours.(solve)
问题描述：
Children often _____solution to the problem required many hours.(solve)
答
solve
原因如下：分析句子成分,句子中有两个动词solve和require,通过分析后,solve是谓语,required many hours来充当定语从句,另,从foten可知时态用一般现在时,主语children是复数,因此用动词原形.