If $${L_1} = \left\{ {{a^n}\left| {n \ge \left. 0 \right\}} \right.} \right.$$ and $${L_2} = \left\{ {{b^n}\left| {n \ge \left. 0 \right\}} \right.} \right.,$$ consider
$$\left. {\rm I} \right)$$ $$\,\,\,{L_{1 \bullet }}{L_2}$$ is a regular language
$$\left. {\rm II} \right)$$ $$\,\,\,{L_{1 \bullet }}{L_2} = \left\{ {{a^n}{b^n}\left| {n \ge \left. 0 \right\}} \right.} \right.$$
Which one of the following is CORRECT?

Consider the languages $${L_1} = \phi $$ and $${L_2} = \left\{ a \right\}.$$ Which one of the following represents $${L_1}\,L_2^ * UL_1^ * ?$$

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

Let $${L_1}$$ recursive language. Let $${L_2}$$ and $${L_3}$$ be languages that are recursively enumerable but not recursive. Which of the following statement is not necessarily true?