The sum of all probabilities given in the table must be equal to 1.
We know the probabilities of 3 outcomes, using them we can find the probability of the fourth outcome.
P(4) = 1 - P(Not 4)
=1 - [ P(1) + P(2) + P(3)]
= 1 - (0.4 + 0.2 + 0.15)
=1 - 0.75
P(4) = 0.25
Thus the answer is option B
