How clear will a red warning symbol be on a dark orange background?

Correct answer: Limited because the hues are close and values may be similar

The governing concept is colour contrast, which depends on hue and value rather than colour names alone. Red and orange are neighbouring warm hues, so they may not separate strongly; if both are dark, their value difference is also small. The warning symbol can therefore have limited readability, making B correct. They are not complementary, and texture or black-and-white contrast is not guaranteed.