A bag contains 4 red marbles, 6 blue marbles, and 5 green marbles. If one marble is chosen at random, what is the probability that it is a blue marble?

✓ Correct Answer: Option B

Calculate the total number of marbles: 4 + 6 + 5 = 15. There are 6 blue marbles. The probability of choosing a blue marble is 6/15, which simplifies to 2/5.