What is the shape and color design of a mandatory (command) sign?

What is the shape and color design of a mandatory (command) sign?

1. Circular shape with a thick red inner border, thin white outer border, and a black symbol on a white background
2. Square shape with a thick blue inner border, thin white outer border, and a yellow symbol
3. Circular shape with a white border, blue background, and a white symbol

Correct answer

Circular shape with a white border, blue background, and a white symbol

This is the correct answer for the Cambodian driving theory test. Questions are drawn from the official Ministry of Public Works and Transport sign library and road rules.