I'd say (2) also.
I quick method... 10^25 - 7 will give all 9's except the last digit. This value is divisble by 3 leaving 1 in the answer. On basis of that I figured since all 9's will be divided evenly by 9, last three won't be. So you end up with 1/3.
b)3 is the correct answer.
its not divisible by 2, last digit is 3
its not divisible by 9 , as the sum of digits is 9*24 +3 = 219 ...which is not divisible by 9
Sum of digits is divisible by 3 ,so yes, 3 is the answer.