What is an adaptation?

a. a dog learns to roll over.
b. a cat learns to eat from a bowl.
c. a horse breaks its leg while running.
d. a camel has humps that store fat.

D. A camel has humps that store fat.

Explanation:

In Biology "adaptation" refers to one or more traits that originated from changes in living beings that improved their fitness and ability to survive in a certain environment. These traits or "adaptations" are passed down every generation, from parents to the offspring.

For example, just because a dog X learned how to roll over, that isn't something that he's acquired nor passed down to its offspring. Thus, learning and injuries (option C) are not "adaptations".

Camels, on the other hand, developed those humps that store fat in order to deal better with the extreme conditions they cope with everyday.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).