请问The report advances suggestion that safety standards should be improved.这句话中包含了什么从句

that safety standards should be improved是个that引导的同位语从句
这个从句与suggestion是同等位置的关系，也就是解释了suggestion的内容

报告暗示说安全条件需要提高

定语从句
that safety standards should be improved
它是修饰 suggestion 的

safety standards should be improved 做的是suggestion的同位语成分，因此是同位语从句
同位语从句一般跟在某些名词后面，用以说明该名词表示的具体内容。如：
I heard the news that our team had won．
我听到了我们队获胜的消息。
I had no idea that you were here．
我不知道你在这里。

是由that引导的定语从句 that safety standards should be improved修饰suggestion这个中心词
如果有中心词，一般是定语从句如：
I don't like the color which is red。
我不喜欢红颜色。
这就是由which引导的定语从句， which is red修饰color。 而color就是中心词。

是由that引导的定语从句 that safety standards should be improved修饰suggestion