Oxygen accounts for about of the air in the atmosphere. A: 82%

B: 5%

C: 66%

D: 53%

E: 21%

To determine if a particular plant is homozygous or heterozygous, you would have to test cross with a

Which of the following types of pollution is most responsible for large numbers of deaths worldwide because of unsafe drinking water? (a) nutrient pollution (b) thermal pollution (c) pathogen pollution (d) sediment pollution

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.