(whether)this material can be used in our factory has not been studied yet 括号里为什么不能用that如题,

(whether)this material can be used in our factory has not been studied yet 括号里为什么不能用that如题,
(whether)this material can be used in our factory has not been studied yet 括号里为什么不能用that
如题,

(whether)this material can be used in our factory has not been studied yet 括号里为什么不能用that如题,
主语从句.whether有是否的意思,that引导主语从句,补充当句子成分,不翻译.

whether 表示疑问，意思是，此材料能否在我厂使用，尚未研究。而that 一般用于肯定句式，所以用于本句不恰当。