Why, according to the passage, is biogas introduced to poor people?

Energy is fundamental to human beings, especially to poor people – the one-third of humanity that does not have modern energy supplies like electricity or natural gas, with which their life could be improved.

Many people who live in countryside and mountainous areas have to gather fuel wood.  This takes a lot of time.  Moreover, it causes indoor air pollution because of heavy smoke.  For many people living in rural areas in developing countries of the world, biogas is the large energy resources available and costs almost nothing.  The main use of biogas is for cooking and heating, but it can also provide energy for public transport.  As biogas is smoke-free, it helps solve the problem of indoor air pollution.  Moreover, plant waste and animal manure cost almost nothing.

The tendency to use renewable energy sources in developing countries is on the increase when non-renewable ones are running out.  In the near future, people in the developing countries may use wind or sea waves as the environment-friendly energy sources.

Human beings (24) __________ to protect only the beautiful and non-threatening parts of our environment.  We tend to pay more (25) ________ to animals on land than any other large sea animals.  Environmentalists have not done much enough to help save the Pacific Ocean sharks (26) _________ population has decreased nearly to the point of extinction.

Sharks are among the oldest creatures on Earth, having survived in the seas for more than 350 million years.  The fact that they have managed to live in the oceans for so many millions of years is enough proofs of their efficiency and adaptability to change environments.

It’s time (27) _________ human beings to begin considering the protection of sharks as important part of a program for protection of our natural (28) __________.