The answer is D. 5/8.
You have to divide the second event by the first event, so you have to divide 1/4 by 4/10.
You can just put that into your calculator and get 5/8, or you can multiply 1/4 by the reciprocal of 4/10, which is 10/4.
1/4 times 10/4 equals 5/8, therefore, the answer is 5/8.