The children talked and laughed on and on______(happy).
问题描述：
The children talked and laughed on and on______(happy).
答
The children talked and laughed on and on happing
答
happily
on and on 是一直的意思，happily副词修饰动词talk和laugh。
句意是：孩子们愉快地交谈着，欢笑着。
答
happily
这里需要一个副词修饰动词talk和laugh,而on and on 实际上可以做一个短语,意为“不断地,不停地”
答
happing