Question

the european garden snails that live in fields and hedges have yellow shells with stripes, whereas those that live in wooded habitats have brown shells without stripes. why does natural selection favor genetic variation among european garden snails occupying different habitats?
it helps the snails avoid being seen by predators.
it helps the snails adapt to different feeding behaviors.
it helps the snails maintain a constant body temperature.
it helps the snails limit themselves to a particular habitat.

Explanation:

Natural selection acts on traits that provide a survival advantage. Snails with shells that match their habitat (e.g., yellow - striped shells in fields/hedges, brown shells in wooded areas) are less likely to be seen by predators. This trait variation is favored as it increases the snails' chances of survival and reproduction. Traits like body temperature maintenance (snails are ectotherms and don't maintain a constant body temperature), adapting to different feeding behaviors (not directly related to shell color variation in this context), or limiting themselves to a particular habitat (the question is about why different shell types exist in different habitats, not about habitat limitation) are not the main reasons for the observed shell color variation due to natural selection.

Answer:

It helps the snails avoid being seen by predators.