Consider the following statements: S1 : Let L be language, reversal of language L cannot contain any string present in ‘L’ except ‘∈’. S2 : Concatenation of two different language cannot be commutative until atleast one of them is ‘Φ’ or ‘∈’. Which of the following is correct?

Consider the following language over Σ = {0, 1}:L = {<M>|M is TM that accept all strings of length at most 5} Which of the following is true? (A) Decidable and REC (B) Undecidable and RE (C) Undecidable and non RE (D) Decidable but RE

Consider statements: S1 : A finite lattice is always bounded. S2 : Complemented lattice is a proper subset of bounded lattice. S3 : A bounded and complemented lattice may or may not be a distributive lattice. Which of the following is/are true? A.) S1 and S2 only B.)S2 and ... S2 and S3 Answer is D as per the solution my doubt is a lattice can be semi bounded and not Bounded then why S1 is true.