There's are a few rules going around here, and we need to figure out what those are to accurately answer this question.
For starters, we have a < b < c, with a being greater than 10. I also see that we're looking at a remainder for a^c / b, and a, b, c are all consecutive integers.
That means, a^c will be monstrously large - so we need to figure out things more logically.
Still, to assume things, I'd go with a = 100, b = 101, and c = 102. That means, we're looking for the remainder of 100^102 / 101. Now, here, the 100, whatever it is raised by, will give us a number that's a few gazillion bazillion and whatnot... with multiple zeroes at the end.
But is there a pattern to the remainders? We know such patterns can help negate any complete math.
I know divided 100 by 101 won't help in anyway, so I'll go for 100^2 / 101; that's 10,000 / 101. A bit of manual long-division - 1,000 / 101 leaves a remainder 91; 910 / 101, leaves a remainder of
1. But will this remainder of 1 stay even in subsequent powers of 100? We can take: 1,00,000 / 101. A bit of manual long-division - 1,000 / 101 leaves 91; then 910 / 101 leaves 1, to which if we add the remaining three zeroes, we'll again arrive at a remainder of 91. Oops, it isn't 1.
Should we see 100^4? That's 100,000,000. Now, here - and trust me, this is the last of the complex maths - you realize that for each 10,000, dividing by 101 will give a remainder of 1, so as long as we're dealing in powers of 10,000, we'll get a remainder of 1. 100,000,000 = 10,000*10,000; so a remainder of 1.
In other words, for each EVEN power of 100, we'll get the remainder as 1.
That'll hold true for 100^102.
But you must have noticed, that the rules change for every odd power.
So, what will happen if we, instead, need to look at an odd set of numbers?
For the this, and for the sake of simplicity, we can go down to the smallest numbers that are permissible - 11, 12, and 13, as a, b, and c.
Now, we need the value of 11^13 / 12. As we're looking at odd powers, we can attempt to find a pattern with, first, 11^1. This, when divided by 12, will simply give us 11 as a remainder.
But for 11^3, which is 1331, when we divide this by 12, we get a remainder of - well, what do you know, 11 (easy long-division proves that).
If we continue doing the same, the 11 remainder sticks.
So, for odd powers, clearly, the remainder is b - 1 (as b = 12 here). And for even powers, the remainder is, clearly, 1. The answer is D = I & II only.Bunuel