What is the complement of the language accepted by the $$NFA$$ shown below?
Assume $$\sum { = \left\{ a \right\}\,\,} $$ and $$\varepsilon $$ is the empty string.

Consider the set of strings on $$\left\{ {0,1} \right\}$$ in which, every substring of $$3$$ symbols has at most two zeros. For example, $$001110$$ and $$011001$$ are in the language, but $$100010$$ is not. All strings of length less than $$3$$ are also in the language. A partially completed $$DFA$$ that accepts this language is shown below.

The missing arcs in the $$DFA$$ are

Which of the following problems are decidable?
$$1.$$ Does a given program ever produce an output?
$$2.$$ If L is a context-free language, then, is $$\overline L $$ also context-free?
$$3.$$ If L is a regular language, then, is $$\overline L $$ also regular?
$$4.$$ If L is a recursive language, then, is $$\overline L $$ also recursive?