Answer:
Momentum of car and Earth as a system will remain conserved
Step-by-step explanation:
As we know that momentum conservation is applicable when system has no external force on it
So here we will say

now we know that
if we will have F = 0

so here we can say

now since Earth and car as a whole system is considered then there is no external force on that system.
So here momentum as a whole will remain conserved.