Concept:An environmentally friendly (clean) energy source produces little or no pollution when it is used.
Solution:I. Wind: turbines turn wind into electricity with no smoke or gases. Clean.
II. Hydro: falling water turns turbines (e.g. Akosombo Dam) with no burning and no smoke. Clean.
III. Biomass (firewood, charcoal, crop waste, dung) is renewable, but it is used by burning, which gives off smoke, soot and carbon dioxide, and cutting trees for firewood and charcoal causes deforestation in Ghana.
So only wind and hydro are environmentally friendly.
Key point: Renewable does not always mean clean. Biomass is renewable but polluting when burnt.
Answer:Option C (I and II only)