Which statements about PDA stacks are correct?
A PDA has an unbounded stack and may use $\epsilon$ moves; standard definitions allow replacing the top by a finite string.
The classic grammar S -> iEtS | iEtSeS | a is ambiguous because of which phenomenon?
An else can be associated with more than one unmatched if.
A grammar with productions S -> AB, A -> a, B -> b is in which normal form?
S -> AB is binary and A,B -> terminal satisfy CNF.
What is the maximum number of PDA transition-domain combinations if |Q|=3, |$\Sigma|=4$ and |$\Gamma|=5, using Q x (\Sigma union {\epsilon}) x \Gamma$?
There are 3*5*5 = 75 possible triples.
Which general CFG decision problem is known to be undecidable?
Whether a CFG generates $\Sigma*$ is undecidable.