3. Read the following passage and then answer the questions that follow.
Natural resources can be classified as nonrenewable and renewable. Nonrenewable or exhaustible resources such as fossil fuels, copper, and gold exist in fixed amount in various places in the earth crust. They can be used completely or economically depleted to the point where it costs too much to get what is left, when 80 percent of its total estimated supply has been removed and used.
A renewable resource is one that can theoretically last forever, because it is replaced through natural process. Examples are trees in the forest, grasses in grasslands, wild animals, fresh surface water in lakes and rivers, fresh air and fertile soils. The earth most valuable resources, is its diversity of potentially renewable forms of life. But over use can convert renewable resources to nonrenewable by using them faster than they can be replenished.
Some nonrenewable resources can be recycled or reused to extend supplies. Iron, aluminium, glass, for example, can be collected, remelted, reprocessed and made into new products. Also to avoid excessive use of resources, recycling of papers products needlessly burned or thrown away, reduce timber needs for the paper industry. Domestic refuse can be used to generate power particularly for local districts heating and lighting schemes, though care must be taken when incinerating to avoid air pollution problems.
Other nonrenewable resources, such as fossil fuels (coal, oil and natural gas), cannot be recycled or reused. When burned, the high quality useful energy in these fuels is converted to low quality waste heat and exhausted gases that pollute the atmosphere.
(a) From the passage, identify two resources which can be replaced through the natural process.
(b) State three merits of recycling nonrenewable resources.
(c) List down three environmental problems associated with burning of fossil fuels.
(d) Explain the condition under which renewable resources cannot be renewed.
(e) Suggest two measures to promote sustainable use of natural resources.