Read for the main message
Son compares energy sources at his secondary school during the lunch break. Son does this because he wants to explain energy choices clearly. His display contrasts coal with sunlight and wind. Coal is non-renewable: it takes a very long time to form, and burning it releases pollution and carbon dioxide. Sunlight and wind are naturally replenished, but their output changes with weather and time of day. No source is described as free of every environmental cost. The class discusses benefits and limitations before making a choice.
Read first for the main message, then scan for a detail. Point to the sentence supporting each answer; do not substitute a general belief for evidence from this text.