Runoffs from an uranium mine stockpile have contaminated the surface water in a location. this might cause health problems among people in the location. which of these is the best plan to solve this problem?

a-plant trees around uranium mines to absorb contaminants
b-put fences around uranium mines to check the flow of contaminants
c- wear protective clothing for prevention against harmful effects of radiation
d-collect the runoffs in retention ponds for isolation and recovery of contaminants

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.