Given,
L1 = {a^n b^n c^m d^m | n, m>=0} = {ɛ, ab, cd, abcd, aabb, ccdd,…..}
L2 = {a^n b^n | n>=0} = {ɛ, ab, aabb, aaabbb, …..}
L3 = {c^m d^m | m>=0} = {ɛ, cd, ccdd, cccddd, …..}
Now, L2.L3 = {ɛ, ab, aabb, aaabbb, …..} . {ɛ, cd, ccdd, cccddd, …..}
= {ɛ, ab, cd, abcd, aabb, ccdd, aabbcd, aabbccdd ….}
see, L2.L3 contain all the element which is present in L1
so, L1 – L2.L3 = {} (empty set) which is regular
As L1 – L2.L3 is regular so its CFL, CSL, REL
Hence all option is correct