Consider the following non-deterministic automaton, where s1 is the start state and s4 is the final (accepting) state. The alphabet is {a, b}. A transition with label can be taken without consuming any symbol from the input.
Which of the following regular expressions corresponds to the language accepted by this automaton?
1
(a + b)*aba
2
aba(a + b)*aba
3
(a + b)aba(b + a)*
4
aba(a + b)*