Hello! The correct answer is the first choice.
You are correct that the second and fourth choices are incorrect. This is because these are negative - they cause harm towards a population (can't groom themselves and can't cope with low water conditions) and therefore do not favor the survival of an organism.
The third choice is incorrect because while developing webbed feet is an adaptation, it does not favor the survival of the organism. This is because we see that the population of the squirrels is a ground population, meaning that they stick to the land. This means that they would have no use for webbed feet.
However, the first choice is correct. Camouflaging abilities would aid the butterflies' survival as it would increase their chances of hiding from predators. Therefore, it is an adaptation which favors the survival of the butterflies.
Hope this helps!