A 3.0 \mathrm{~kg} ball moving at 10 \mathrm{~m} / \mathrm{s} east collides elastically with a 2.0 \mathrm{~kg} ball moving 15 \mathrm{~m} / \mathrm{s} west. Which of the following statements could be true after the collision?
Answer Choices
A. The two balls are both moving directly east.
B. The 3.0 \mathrm{~kg} ball moves directly west at 15 \mathrm{~m} / \mathrm{s}.
C. The 2.0 \mathrm{~kg} ball moves directly north at 10 \mathrm{~m} / \mathrm{s}.
D. The 3.0 \mathrm{~kg} ball is at rest.
E. The 2.0 \mathrm{~kg} ball moves directly south at 15 \mathrm{~m} / \mathrm{s}.