A good research question should always be

a. controversial.

b. expansive.

c. multifaceted.

d. obscure.

It should not be controversial: it would only make the research less reliable since people would have their opinions about the topic that they would want to defend. It should also not be obscure: then it's hard to check.

The best answer is that it should be multifaceted: it should include a number of aspects, not just one, so that the test can check for those aspects, not just one.