If you cant answer all sub questions please answer part a

Problem 4 (30): Prove that the following languages are not regular. (a) L1= {a b c | n 2 0} (b) L2 = {WWR | W,WR {a, b}* and wp is the reversal of w} (c) L4 = {w | we {a, b}* and the number of a's is greater than the number of b's}