Final answer:
Regulatory signs with 3-sided red letters on a white background are triangular in shape, indicate mandatory actions or restrictions, and are crucial for safe and legal driving. The correct answer is 4) All of the above.
Step-by-step explanation:
The characteristics of regulatory signs with 3-sided red letters on a white background are as follows:
- They have red letters on a white background.
- They are triangular in shape.
- They indicate mandatory actions or restrictions.
When encountering such signs on the road, it's important to adhere to the indicated commands to ensure safe and legal driving. These signs are designed to inform road users of critical regulations they must follow.
In conclusion, the correct answer would be 4) All of the above, as these signs combine a specific color and shape scheme with the purpose of communicating road rules that must be obeyed.