Final answer:
High beam headlights should be used in foggy conditions, and low beam headlights should be used in other situations such as rain, snow, and energy conservation.
Step-by-step explanation:
In the situation you would use the high beam headlights when it is foggy. High beam headlights help improve visibility in foggy conditions as they provide a wider and brighter light beam. In the other situations mentioned, such as rainy, snowy or when conserving energy, it is recommended to use the low beam headlights.