Which of the following identifies NATO NBC defense signs?

The identification of NATO NBC defense signs is crucial for understanding the types of threats that may be faced during military operations. The correct identification for chemical threats is represented by yellow signs with red letters. This specific color combination stands out and is easily recognizable, facilitating immediate understanding and action by military personnel. Each color and graphic design in the signs is specifically chosen to ensure clarity and effectiveness in communication during critical situations.

Chemical agents, being one of the primary threats, necessitate a clear and distinct identification system. This is why the use of yellow for visibility combined with red letters, which generally signify warning or danger, makes this identification effective and vital for quick recognition in the field.

Other options represent different kinds of threats or are incorrectly matched in their color combinations, which might lead to confusion or a delayed response in scenarios involving NBC threats.