as we know recursive language are closed under complementation hence L1 is recusrive language so L1' also and it is also recusrive enumerable language
( all options are still open as all satisfy above property )
recursive enumerable language are not closed under complementation so it may be recursive enumerable language or not
case 1: if L' is recursive enumerable language
as we know if L and L' are recursive enumerable languages then L is recursive language but here in question they mentioned L2 is not recusrive
hence L2' cant be recursive enumerable language
therfore L2' accept only case 2 which is L2' is not recursive enumerable language
Ans is B