For the answer to the question above,
the answer is "The student can have only one blood type, so the actual events are mutually exclusive. "
The probabilities are not mutually exclusive. Based on the group
P(Type O) = 9/20 = 45% or 0.45
P(Type A) = 2/5 = 40% or 0.40
P(Other) = 3/20 = 15% or 0.15
I hope my answer helped you. Feel free to ask more questions. Have a nice day!