L1 is not regular we will not have the string in A.P only a,a^4,a^9,......
L2 is regular i.e if m=2 a^2,a^4,a^8,.....
L3 is also regular only i.e p1= (( a 2 ) n) * is regular
p2=(( an )2 )* is also regular only
concatenation of two regular is regular only.