GATE Computer Science (CS) 2019 Solved Papers

If L is regular, L⋅LR is also regular by closure property.
Suffix (L) and Prefix (L) are also regular by closure property.
However option (b) {wWR∣w∈L} need not be regular since if L is an infinite regular language, then {wwR∣w∈L} will not only be infinite, but also non-regular. Since it involves string matching and we can increase in length indefinitely and then finite automata FA will run out of memory.