Which one of the following regular expressions represents the language: the set of all binary strings having two consecutive 0s and two consecutive 1s?

Let L1 and L2 be any context-free language and R be any regular language. Then, which of the following is correct ? I. L1 ∪ L2 is context-free. II. L1' is cont...

For Σ = {a, b}, let us consider the regular language L = {x ∣ x = a2+ 3k or x = b10 + 12k, k ≥ 0} Which one of the following can be a pumping length (the co...