A Researcher Plans to Study the Relationship Between People's Smoking

A researcher plans to study the relationship between people's smoking behavior and their tendency to have minor physical illnesses (such as colds or the flu) . MOST likely, he will use correlational research for the study because

A) correlational studies are always the "first choice" of researchers.
B) it is not practical or ethical to manipulate people's smoking behavior.
C) correlational studies allow the researcher to draw strong cause-and-effect conclusions.
D) the university does not allow smoking in the psychology building.