Step 1: Concept
Check if the integrand is an even or odd function over a symmetric interval $[-a, a]$.
Step 2: Meaning
An odd function $f(x)$ satisfies $f(-x) = -f(x)$. The integral of an odd function from $-a$ to $a$ is zero.
Step 3: Analysis
Let $f(x) = (x^5 + x^3 + x)\cos x$.
$f(-x) = ((-x)^5 + (-x)^3 + (-x))\cos(-x) = (-x^5 - x^3 - x)\cos x = -f(x)$.
Step 4: Conclusion
Since the function is odd, the integral is 0.
Final Answer: (E)