This is the 15702nd most frequent Korean word.
보증한
"Guaranteed" or "assured."
In this sentence, "보증한" is used as a past-tense modifier to describe someone who has assured or guaranteed something, specifically trust.
그는 그의 믿음을 저에게 보증한 사람입니다.
He is the person who guaranteed his trust to me.
Here, "보증한" serves as a past-tense modifier for "experts," indicating they vouched for the quality of the product.
이 제품의 품질은 전문가들이 보증한 것입니다.
The quality of this product is guaranteed by experts.
In this sentence, "보증한" is used to express the commitment by a group regarding a course of action.