求能帮我分析一下这个句子的结构，在线等，满意加分！

来源：百度知道 编辑：UC知道 时间：2024/06/14 14:20:19
Did you know that it's been found in laboratory testing that some type of oil are really bad for us?
第一个that 是宾语从句，那第二个that呢，是做宾语还是定语，具体分析下，谢谢！
test在这里做什么用法?是in lab testing还是 find sth doing ,能详细讲解一下吗?再加分!

did you know [that it's been found in lab testing (that some type of oil are really bad for us)].
()里是主语从句，it是代主语，that只是一个引起句子的词，可视为连词。