Simple
Naive
noun, な adjective
People made from simple elements are also pretty simple. And they can be naive too. But that's just how they're built.
そぼく
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
みなさんの素朴な疑問にお答えします。
I'll respond to everyone’s simple questions.