5 Newtons
8 Newtons
10 Newtons
12 Newtons
Answer is Right!
Answer is Wrong!
The correct answer is $\boxed{\text{D}}$.
The resultant of two forces acting at right angles to each other is equal to the square root of the sum of the squares of the two forces. In this case, the two forces are 6 Newtons and 8 Newtons, so the resultant is equal to $\sqrt{6^2 + 8^2} = \sqrt{100} = 10$ Newtons.
Option A is incorrect because 5 Newtons is not the square root of the sum of the squares of 6 Newtons and 8 Newtons.
Option B is incorrect because 8 Newtons is the magnitude of one of the forces, not the resultant of the two forces.
Option C is incorrect because 10 Newtons is the magnitude of the resultant of the two forces.