a) v2=(T2/T1)V1 b) V1T1=V2T2 c)V1/V2= T2/T1 d) V1/T1= V2/T2
3 Answers

Charles' Law States V1/T1 = V2/T2.
So this implies:
V2 = (T2/T1)V1, so we know (a) is true.
V1/T1 = V2/T2, by definition, so we know (d) is true.
Neither (b) or (c) is possible for an ideal gas at constant pressure. But I think you may have mistyped (c). V2/V1 = T2/T1 *is* possible for an ideal gas at constant pressure. So I think you may have reversed the numerator and the denominator.
If this is true, then (b) would be the case that is not possible, and the answer to your question.

both b and c are wrong
because the gas law is PV/T = const
so, when P = const,
V1/T1 = V2/T2 ... which is same as d
by multiplying T2 both sides, even a is derived
so b and c are wrong

Do your own homework. I'll tell you how to solve it, but I won't tell you the answer:
All but one of those equations are algebraically equivalent to one another. So, all you have to do is convert them around by multiplying or dividing by any one of the terms (i.e. V1, V2, T1, or T2), and if you can get one of the choices by manipulating another one, then you know it's either of those. Keep doing it until you've shown that at least three of them are equivalent to each other; the answer is the one that remains.