When formulating research question, a researcher should
a. write a question that has already been thoroughly written about.
b. write a question that is impossible to answer.
c. write a question that can be easily answered.
d. write a question that has an undetermined answer.

When formulating a research question, a researcher should write a question that has an undetermined answer. This is so because researchers' goal is to prove something that has not been discussed, that is, they look for new information. What is there to prove if what you are stating has already been thoroughly written about? What is the point of writing a question that is impossible to answer?

Research is understood as the systematic investigation and the study of several sources so as to establish facts and reach new conclusions.  That is why D is your answer.

the answer would be d. he tells the story through a teenage narrator.