A bag contains 4 red marbles, 3 blue marbles, and 5 green marbles. If you randomly select one marble from the bag, what is the probability that it will be a blue marble?
✓ Correct Answer: Option A
Total marbles = 4 + 3 + 5 = 12. Number of blue marbles = 3. Probability = (Number of blue marbles) / (Total marbles) = 3/12 = 1/4.