Step 1: Concept
The expression $a \sin x + b \cos x$ always lies in the range $[-\sqrt{a^2 + b^2}, \sqrt{a^2 + b^2}]$.
Step 2: Meaning
Therefore, the expression $a \sin x + b \cos x + c$ has a maximum value of $c + \sqrt{a^2 + b^2}$.
Step 3: Analysis
Identify the constants from the given expression: $a = 3$, $b = 4$, and $c = 5$.
Compute the maximum value:
\[ \text{Maximum Value} = 5 + \sqrt{3^2 + 4^2} = 5 + \sqrt{9 + 16} = 5 + \sqrt{25} = 5 + 5 = 10 \]
Step 4: Conclusion
The maximum value that the function can achieve is $10$.
Final Answer: (B)