To find the angle between the two vectors, we can use the dot product formula: $\vec{A} \cdot \vec{B} = AB \cos\theta$. Let's compute the dot product: $\vec{A} \cdot \vec{B} = (3)(3) + (4)(4) + (5)(-5) = 9 + 16 - 25 = 0$. Since the dot product is zero, the angle $\theta$ between them must satisfy $\cos\theta = 0$, which means $\theta = 90^\circ$. The other options are incorrect because a non-zero dot product is required for any angle other than $90^\circ$.