At night, it is **mandatory** for a vehicle's license plate to be illuminated. This is because the vehicle's lights must be on whenever it is nighttime to ensure visibility and safety on the road.

- The vehicle's lights, including those that illuminate the license plate, are essential for other drivers to see and read the license plate from an adequate distance. This is especially important on poorly lit roads, where the license plate could not be read from 10 meters away without proper lighting.

- Additionally, the regulations state that all cars must have two license plates, one at the front and one at the back, and these must be visible at all times, which includes the need to be illuminated at night.

Therefore, the correct answer is **yes**, the license plate must be illuminated at night to comply with road safety and visibility regulations.