The product of uncommon real roots of the two polynomials $ x^4 \plus{} 2x^3 \minus{} 8x^2 \minus{} 6x \plus{} 15$ and $ x^3 \plus{} 4x^2 \minus{} x \minus{} 10$ is ?

$\textbf{(A)}\  \minus{} 4 \qquad\textbf{(B)}\  4 \qquad\textbf{(C)}\  \minus{} 6 \qquad\textbf{(D)}\  6 \qquad\textbf{(E)}\ \text{None}$
1. **Identify the roots of the second polynomial \( Q(x) = x^3 + 4x^2 - x - 10 \):**
   - We start by checking if \( x = -2 \) is a root of \( Q(x) \):
     \[
     Q(-2) = (-2)^3 + 4(-2)^2 - (-2) - 10 = -8 + 16 + 2 - 10 = 0
     \]
     Therefore, \( x = -2 \) is a root of \( Q(x) \).

2. **Factorize \( Q(x) \) using \( x = -2 \):**
   - Since \( x = -2 \) is a root, we can factor \( Q(x) \) as:
     \[
     Q(x) = (x + 2)(x^2 + 2x - 5)
     \]
   - We can verify this by polynomial division or synthetic division.

3. **Identify the roots of the quadratic factor \( x^2 + 2x - 5 \):**
   - Solve \( x^2 + 2x - 5 = 0 \) using the quadratic formula:
     \[
     x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{-2 \pm \sqrt{4 + 20}}{2} = \frac{-2 \pm \sqrt{24}}{2} = \frac{-2 \pm 2\sqrt{6}}{2} = -1 \pm \sqrt{6}
     \]
   - The roots are \( x = -1 + \sqrt{6} \) and \( x = -1 - \sqrt{6} \).

4. **Check if these roots are also roots of the first polynomial \( P(x) = x^4 + 2x^3 - 8x^2 - 6x + 15 \):**
   - We need to check if \( x = -2 \), \( x = -1 + \sqrt{6} \), or \( x = -1 - \sqrt{6} \) are roots of \( P(x) \).

5. **Verify \( x = -2 \) is not a root of \( P(x) \):**
   \[
   P(-2) = (-2)^4 + 2(-2)^3 - 8(-2)^2 - 6(-2) + 15 = 16 - 16 - 32 + 12 + 15 = -5 \neq 0
   \]
   - Therefore, \( x = -2 \) is not a root of \( P(x) \).

6. **Check if \( x = -1 + \sqrt{6} \) or \( x = -1 - \sqrt{6} \) are roots of \( P(x) \):**
   - We need to verify if \( P(x) \) can be factored to include \( x^2 + 2x - 5 \):
     \[
     P(x) = (x^2 - 3)(x^2 + 2x - 5)
     \]
   - This factorization implies that the roots of \( x^2 - 3 = 0 \) are also roots of \( P(x) \):
     \[
     x^2 - 3 = 0 \implies x = \pm \sqrt{3}
     \]

7. **Identify the uncommon roots:**
   - The roots of \( P(x) \) are \( \pm \sqrt{3} \) and the roots of \( x^2 + 2x - 5 \).
   - The roots of \( Q(x) \) are \( -2 \), \( -1 + \sqrt{6} \), and \( -1 - \sqrt{6} \).
   - The uncommon roots are \( \sqrt{3} \) and \( -2 \).

8. **Calculate the product of the uncommon roots:**
   \[
   \text{Product of uncommon roots} = \sqrt{3} \times (-2) = -2\sqrt{3}
   \]

The final answer is \(\boxed{-2\sqrt{3}}\).