How many bronze stars are worn on a ribbon for the second awarding?

The correct choice is one bronze star worn on a ribbon to indicate the second awarding. In the context of military awards, each bronze star signifies an additional award of a medal. The first award is represented by the medal itself, while subsequent awards are denoted by bronze stars. Thus, after the initial awarding of the medal, the subsequent awarding is marked by one bronze star. This system allows for easy recognition of multiple awards for the same achievement without needing to wear multiple medals, simplifying the display on the uniform.