29. A common feature of thermal pollution and artificial eutrophication is that they both
a. have sources that are difficult to identify and control
b. cause large mats of algae to bloom in fresh water
c. are a result of power plants and other industrial activity
d. decrease the amount of oxygen dissolved in water
D?
33. A true statement about the greenhouse gases is that they
a. convert sunlight into heat energy that warms Earth
b. are concentrated in the stratosphere
c. trap heat that is radiated upward from Earth
d. are not affected by human activity
I'm confused beween A and C
42. The critical difference between today's global warming and Earth's previous climate changes is that
a. human-made chemicals such as CFSs do not influence global warming
b. previous changes in climate were dramatic but very short-lived
c. scientist can now save all species from extinction by genetic engineering
d. global warming may occur much more rapidly than it did during previous climate changes due to rising carbon dioxide levels
I think it's D
For question 29, the correct answer is c. Artificial eutrophication and thermal pollution are both caused by power plants and other industrial activities. To get to this answer, you could eliminate options b and d since they do not directly relate to the statement. Option a is not correct because the sources of thermal pollution and artificial eutrophication are typically traceable to specific human activities. This leaves option c as the correct answer.
For question 33, the correct answer is c. Greenhouse gases trap heat that is radiated upward from Earth. To arrive at this answer, you can eliminate option b since greenhouse gases are not concentrated in the stratosphere. Option d is also incorrect because human activity does affect the concentration of greenhouse gases, so the correct answer is option c.
For question 42, the correct answer is d. Global warming may occur much more rapidly than it did during previous climate changes due to rising carbon dioxide levels. To reach this answer, you can eliminate options a, b, and c. Option a is incorrect because human-made chemicals such as CFCs do influence global warming. Option b is incorrect because previous climate changes were not necessarily short-lived. Option c is incorrect because scientists cannot currently save all species from extinction through genetic engineering. This leaves option d as the correct answer.