Given:
Car P and Q are travelling toward each other.
The speed of P is,

Acceleration of car P is,

The speed of Q is,

The cars meet after 5 s.
Acceleration of car Q is,

To find:
The graph of V-T of the cars
Step-by-step explanation:
The slope of v-T graph shows the acceleration of the object.
AS the cars both have acceleration, the speed vs time graph will be a straight line with positive slopes.
The speed of P in 5 s is,

The speed of Q after 5 s,

The graphs will not intersect each other after 5 s.
Hence, the third one is the correct graph.