The scenario that accurately describes magnitude and direction is:
A car traveling northward with 5 kN of force could be brought to a stop by a southward force of 5 kN.
This is because a southward force of 5 kN would exactly counteract the northward force of 5 kN, resulting in a net force of zero, which would bring the car to a stop.
The other options either misrepresent forces (like using kg, which is a measure of mass, not force) or incorrectly state the relationship between the acting forces.