Which Is an Example of a Poor Research Question That

Which is an example of a poor research question that cannot be tested?

A) A researcher is interested in whether a low-calorie diet will be effective for weight loss.
B) How does a particular food additive affect the taste of cough syrup?
C) A company wants to know whether a new cancer drug increases life span.
D) A doctor wants to study the effect of a complimentary physical examination on residents in a low-income neighborhood.