Step 1: Concept
Use the inverse trigonometric identity $\sin^{-1}\theta + \cos^{-1}\theta = \frac{\pi}{2}$.
Step 2: Meaning
The integral simplifies to $\int \frac{\pi}{2} dx$.
Step 3: Analysis
Since $\frac{\pi}{2}$ is a constant, it can be taken out: $\frac{\pi}{2} \int 1 dx$.
Step 4: Conclusion
$\frac{\pi}{2}(x) + C = \frac{\pi x}{2} + C$.
Final Answer: (D)