Which statement about lexicographic enumeration is correct for the standard effective string order?
For the standard length-lexicographic order, recursive languages can be enumerated in order, and such an ordered enumerator yields a decider.
Which problem is decidable for a PDA?
PDA membership is decidable because CFL membership is decidable.
Which statement about LBA membership is correct?
For a fixed input, an LBA has a finite configuration graph, so reachability can be decided.
Which problem is decidable for regular languages?
DFA equivalence is decidable by product construction or symmetric difference.
Which statement about NFA minimization is correct?
An NFA can be converted to a DFA and then minimized, so minimization is decidable.