pls answer only parts c and d. would help a lot if you explained it

Exercise 2.25 Prove that the following languages over the alphabet {a,b} are not regular: a) L = {a" ba3nn #0} b) L = {a"b" a"|n #0} c) L = {abi, n0,i = n or i = 2n} d) L = {www is any string}