Which of the following are non regular?
(a) The set of strings in {a,b}* with an even number of b’s
(b) The set of strings in {a, b, c}* where there is no c anywhere to the left of a
(c) The set of strings in {0, 1}* that encode, in binary, an integer w that is a multiple of 3. Interpret the empty strings e as the number 0.
(d) None of the mentioned