Question:
If \( \vec{a} + \vec{b} + \vec{c} = \vec{0} \), \( |\vec{a}| = \sqrt{37} \), \( |\vec{b}| = 3 \), and \( |\vec{c}| = 4 \), then the angle between \( \vec{b} \) and \( \vec{c} \) is:
- A. \( \frac{\pi}{6} \)
- B. \( \frac{\pi}{4} \)
- C. \( \frac{\pi}{3} \)
- D. \( \frac{\pi}{2} \)