how does googles autonomous vehicle know the distance between itself and the vehicles in front or behind…

Brief Explanations:

LIDAR (Light Detection and Ranging) is commonly used in autonomous vehicles to measure distances by emitting laser light and measuring the time - of - flight of the reflected light. Video cameras can provide visual information but are not the main way for distance measurement. Radar is also used for distance sensing but LIDAR is more precise for close - range in autonomous vehicle applications. Google maps is for navigation and mapping of general routes, not for real - time distance measurement between vehicles.

Answer:

B. LIDAR