A、The increase of atmospheric concentration of CO2. B、The increase in the quantity of acid rain in future. C、A warming effect ca

M: Good morning, Dr Healy. Welcome to "The years to Come".
W: Thank you.
M: Well, what are your predictions about the world? What is it going to be like in the year 2020?
W: Hum, if present trends continue, I’m afraid the world in 2020 will be more crowded [1] and more polluted than the world we live in now.
M: Yes, however, food production is constantly increasing. Don’t you think we will be able to cope with the increase in world population?
W: I don’t think so. Even though production is constantly increasing, the people of the world will be poorer than they are today. For hundreds of millions of the desperately poor, the supply of food and other necessities of life will not be any better. And for many they will be worse, unless the nations of the world do something to change the current trends.
M: What is your estimate of world population in the year 2020?
W: Well, already, [2] world population is about 6,500 million. If present trends continue, that is with the number of births by far exceeding the number of deaths, [2] the world population could approach 7,500 million in 2020.
M: That’s worrying! And what about water?
W: Water is becoming a problem too. Water shortage will become more severe in the future, and due to the increase of births there will be enough water only for half of the population.
M: Which of the present trends do you think will continue over the next decade?
W: Well, significant loss of the world’s forests will continue over the next ten years as the demand for wood for fuel and manufacturers increases. Also atmospheric-concentration of carbon dioxide and other chemicals is expected to increase at rates that could alter the world’s climate due to the "greenhouse effect".
M: The "greenhouse effect"? Could you explain what the "greenhouse effect" is?
W: Sure. Well, [3] the amount of carbon dioxide in the air is progressively increasing and it traps more of the heat of the sun in the atmosphere. This has a warming effect which could change the climate.
M: I see. Is this the only effect of carbon dioxide?
W: No, it isn’t. [4] Carbon dioxide and other chemicals which derive from the use of fossil fuels will also increase the quantity of acid rain which is already damaging or even destroying plants, trees and other parts of our environment. Also, [4] there will be a dramatic increase in the number of species becoming extinct. [5] Hundreds of thousands of species will be lost because of the loss of their habitat.
M: That’s appalling! Doctor, thanks for giving us the information.
1. Which of the following is one of Dr. Healy’s predictions?
2．According to Dr．Healy，how many people will be increased by the year 2020?
3．What is the“greenhouse effect”?
4．Besides the“greenhouse effect”, what else will carbon dioxide bring about?
5．What is the direct cause of lots of species’ extinction?