Answer:
The correct answer is option a.
Explanation:
Conservation of momentum :

Where :
= masses of object collided
= initial velocity before collision
= final velocity after collision
We have :
Two equal-mass carts roll towards each other.

Initial velocity of 
Initial velocity of
(opposite direction)
Final velocity of
(same direction )
Final velocity of
(same direction)


v = 0.5 m/s
rg135
The speed of the carts after their collision is 0.5 m/s.