Catching the condition given in the question that "exactly two of the p, q and r are true and is false otherwise."
by solving option (b) like (1 1 1) ^ (1 1 1) v (0 0 0) = (1 1 1) also gives true but,
Option (c) is correct because it matches the condition given in the question having exactly two of p,q and r are true.
Hence, option (c) is correct.