The delivery van arrives at an office every day between 3 PM and 5 PM. The office doors were locked between 3:15 PM and 3:35 PM. What is the probability that the doors were unlocked when the delivery van arrived?

A. 5/6

B. 5/12

C. 1/3

D. 1/6

well we know there is a gap of 2 hours when the delivery van can come that is the same as 120 minutes we also know that out of that 120 minutes, 20 minutes the doors will be locked so we minus this from the total hours it is open 120 - 20 = 100 this means out of 120 minutes there is 100 minutes where the doors will be open which gives us the probability 100/120 after simplifying this you will get the answer 5/6.

So A. 5/6 is the answer.