Which of the following is a characteristic of junmai sake?

Junmai sake is defined by the absence of added alcohol, which is a distinctive characteristic that separates it from other types of sake. This type of sake is made purely from rice, water, yeast, and koji mold, adhering to traditional brewing methods that do not allow for any distilled alcohol to be introduced during the fermentation process. This results in a sake that emphasizes the natural flavors of the rice and produces a fuller, richer taste profile.

The other characteristics mentioned in the options are not applicable to junmai sake. While some sakes may have added sugar or alcohol to enhance flavor or adjust alcohol content, junmai specifically does not allow for this. The aging of sake varies widely; while some may be aged, it is not an inherent characteristic of junmai. Additionally, carbonation is not typical for junmai, as it is not often produced with this feature. Therefore, recognizing junmai sake's essential quality of having no added alcohol is key to understanding its unique identity within the broader sake category.