That most lakes have been seriously polluted are said by people.从句已经是被动了,就是主句改成被动啊,由that引导主语从句~~
人们说,几乎所有的湖都被严重的污染了.宾语从句,把人们说的内容用一个句子来承担.人们说(People say) 主谓,说了什么?说几乎所有的湖都被严重的污染了.(_most lakes have been seriously polluted)这是宾语,由that连接.
it is said that most lakes have been seriously polluted.