Option (B) 30°
$7 + 4\sin\theta = 9 \Rightarrow 4\sin\theta = 2 \Rightarrow \sin\theta = \dfrac{1}{2}$. Since $\sin 30° = \dfrac{1}{2}$, therefore $\theta = 30°$.
Solve the equation to find $\sin\theta = \frac{1}{2}$, then use the standard values table (Table 8.1) from Chapter 8. Remember $\sin 30° = \frac{1}{2}$ is a must-memorise value. Always show the algebraic step before stating the angle.