A project in Kenya is using biogas（沼气）technology to attack two major pollution problems with one device：a machine that changes waste such as invasive water hyacinth（入侵性水葫芦）into cleaner cooking fuel.
The project from Biogas International,a Kenyan energy technology company,has so far provided 50 of the Flexi Biogas devices to homes in the city of Kisumu in western Kenya.The main device is called a digester（浸煮器）because it breaks down plant waste to produce gas.The digesters will permit families to stop using wood or coal,both of which produce dangerous smoke.People will also be able to cook foods faster using the gas.Tony Otieno used the gas from a digester to cook tea for his 70-year-old grandmother Margaret.He said, "The gas has no smoke,does not smell,and it is much faster than the jiko（a stove that uses wood-coal）."
Some of the families received a gas stove as part of the project,to replace their jiko.The machines process plant waste such as water hyacinth.That plan has covered large parts of Lake Victoria.The weed-like plant harms living things in the lake including fish.The plant also helps bacteria and mosquitoes increase,causing health risks to local communities.
Dominic Wanjihia Kahumbu is head of Biogas International.He said that at a cost of ＄650，most families in the city do not have enough money to buy the device.Although the technology can be on a small or large scale,he said,each system costs a lot to make.As a result,it is unlikely that the company will make a profit for at least another five years.He said the company needs new investment.
Two larger versions of the equipment are still in the testing stage.They would produce clean fuel on an larger scale for restaurants,chicken farms and fish drying facilities in the area.



What do the two major pollution problems refer to？ ______

A. Bacteria and mosquitoes.
B. Plant waste and fuel pollution.
C. Biogas and water hyacinth.
D. Jiko and dangerous smoke.

Which of the following can best describe the device？ ______

A. Large.
B. Cheap.
C. Environment-friendly.
D. Nice-looking.

What can we know about the water hyacinth from the text？ ______

A. It helps fish increase.
B. It has covered Kenya.
C. It's a threat to the local people.
D. It leads to the invention of digester.

What does paragraph 4 mainly tell us about the device？ ______

A. Its kinds.
B. Its disadvantages.
C. Its future.
D. Its function.