Answer
matched hypothesis: (b)
null hypothesis: $H_o: \mu = 3$ (see graph below).
Work Step by Step
The alternative hypothesis $H_a:\mu \ne 3$ means that $\mu$ takes on all values except for $3$, and that is represented by graph (b).
The null hypothesis is the opposite: $H_o: \mu = 3$. See the graph above.
