To prove that the given wff isn't a tautology we need to get False value. For A -> B, we need to get T -> F case.
A. q=F, p v q need to be T, q is F, p we can set as T. T v F = T , so T -> F. Hence not a tautology.
B. p = F, q=T. p v (q -> p) => F v (T -> F) => F
C. p = F, p -> q need to be false. But as p is T, we can never get it at F. Suppose we set p = T, then expression is always T.
So C is correct.