To answer this question, we need to understand that it is a riddle or a joke, rather than a factual question. The answer to this question is not based on any logical reasoning or knowledge about monkeys or baseball.
The correct answer is:
D. APRIL - This option is the correct answer because it plays on the common phrase "April Fools' Day," which is observed on April 1st. April Fools' Day is a day when people play pranks and jokes on each other. Therefore, the question is meant to be a joke, implying that monkeys play baseball on April Fools' Day.