Question

an oil spill occurred in 1969 near the wild harbor salt marsh. researchers have found that several species of salt water marsh plants no longer grow in this area. what is the most likely explanation for these results?
all of the original species have hybridized with new ones.
pollution from the spill has changed the composition of the marsh.
carbon dioxide levels have decreased over the years.
the scientists measured the plants incorrectly.

Explanation:

An oil - spill is a form of pollution. Pollution can alter the chemical and physical composition of an environment like a salt marsh, making it unsuitable for certain plant species to grow. Hybridization would not directly cause the disappearance of original species in this context. Decrease in carbon - dioxide levels is not related to the oil - spill event. And there is no indication that measurement error is the cause.

Answer:

Pollution from the spill has changed the composition of the marsh.