I don't believe that - little children can finishe this task

第一个空填such,such是形容词,后面接名词,本题中即children.
第二个空也填such,
so是副词,后面加形容词.
但本题中little children,中心词是children,little跟such两个形容词一起修饰children.
such a short time 与such little children用法类似.