题目内容：

The general public has very little idea of what agriculture is about.这里为什么用of what?

优质解答

have very little idea of...对某方面知之甚少.
只有what才能做双重成分,即介词of的宾语和介词about的宾语（换成正常语序about what agriculture is就能看出来了） .
所以用of what.