Answer:
The blank is SOURCES
Explanation:
Sources of energy can either be RENEWABLE OR NON-RENEWABLE. Renewable sources of energy are those sources which are easy to replenish while non-renewable sources are difficult to replenish after being exhausted.
Biomass, which comes from plants and animals are considered to be SOURCES of renewable energy because they renewable energy because they take time to grow and require careful planning to ensure continued supply. Trees get their biomass from sun energy, which is a renewable source of energy.
