2. The man is always looking for resources to provide
energy.
The most traditional ones are:
Coal.
Oil
But both are dangerous for the environment.
They pollute the atmosphere. Besides, they are non-
renewable sources.
3. There are two other kinds:
Hydro-electric energy
Nuclear energy
Some experts and environmentalists do not approve
them. Hydro-electric dams can alter the environment and
the life in the rivers and lakes. Nuclear power stations are
not safe and produce dangerous waste.
4. The renewable sources, also called clean
energies, are the cheapest, safest and most
convenient.