Answer:
(A) Because event B rules out obese subjects.
Step-by-step explanation:
(A) is correct because B doesn't have obese people
(B) is incorrect because we don't know if there are obese person but not overweight.
(C) states a correct fact but that portion doesn't relate to event B (overweight but not obese)
Similarly, (D) also states a correct fact but doesn't relate to event B (overweight but not obese)