Are the following True or False. In either case, provide a justification for your answer.

a) any NPDA can be transformed into an equivalent DPDA

b) Any DPDA can be transformed into an equivalent NPDA

c) Like the string pumping lemma for regular languages, the strong pumping lemma for context-free languages allows us to only consider partitions involving the first p symbols (where p is the pumping length).

d) The stack of a PDA can be empty at the start and stop of processing, but will always have at least one symbol on the stack at intermediate times.