Discuss how reproductive strategy affects the structure of a population (in other words, compare and contrast r-selection VS k-selection). In your answer, you should provide examples and discuss: the number of offspring and the amount of parental care.

In an r strategy, the reproduction rate will be high, and therefore the natural selection acts on the first stages of development.  

In a k strategy, the reproduction rate will be lower. Therefore, in this strategy, the selection acts on adult organisms, impacting on its fecundity (i.e., its ability to reproduce)

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."