When formulating a research question for an informative essay, a writer should write a question that
can be answered with a sentence.
has a widely known answer.
has an open-ended answer.
is difficult or impossible to answer.

C.  has an open-ended answer.

Explanation:

A open-ended answer is where it cannot be answered by a yes or no.

Making it interesting and curious, were people want to read what you have written.

They don't want a question to widely know, but not to narrow for multiple paragraphs. And of course they want you to answer and the question.

where is the picture of the graph or table?

a. i just did this quiz and the answer is a.