Two equal masses `m_1` and `m_2` moving along the same straight line with velocites `+3 m//s` and `- 5 m//s` respectively collide elastically. Their velocities after the collision will be respectively.
A. `+ 4 m//s` for both
B. `- 3m//s` and `+ 5 m//s`
C. `-4 m//s` and `+ 4 m//s`
D. `-5 m//s` and `+ 3 m//s`