It is___that the impostors knew little about the invention为什么选certain而不选sure、surely、certainly谢谢哈~

It is___that the impostors knew little about the invention为什么选certain而不选sure、surely、certainly谢谢哈~
It is___that the impostors knew little about the invention
为什么选certain而不选sure、surely、certainly谢谢哈~

It is___that the impostors knew little about the invention为什么选certain而不选sure、surely、certainly谢谢哈~
首先跟在be动词后及在句中位置判断要填形容词,排除两个-ly,其次,sure是跟在人做主语后的,如I'm sure,he's sure

certain 固定用法，
首先这里是形容词，所以排除surely和certainly
其次sure一般是人sure
所以是certain