英语句法问题

Question

A rectal study, published in last week's Journal of the American Medical Association, offers a picture of how risky it is to get a lift from a teenage driver.这句话中‘how risky it is to get a lift from a teenage driver’做的是什么成分？是定语还是补语？麻烦再附带分析，谢谢！！

Answer 1

做介词of的宾语从句。

A rectal study （主语 ） published in last week's Journal of the American Medical Association（过去分词短语作定语） offers（谓语）（ a picture）（宾语） of（ how risky it is to get a lift from a teenage driver.）宾语从句。追问

那么为什么不能看做a picture的宾语补足语呢?谢谢!!

追答

offer sth .
offer sb sth .
offer sth to sb 不加宾语补足语。
不是所有的动词都可加补足语的

Answer 2

正常顺序是:it is how risky to get a lift from a teenage driver.是表语.;真正的主语是动词不定式.