Answer: they grow bigger and stick together
Explanation:
The actual answer is, "A", an ocean trench.
You can find out more about them by researching them up on Google, it's only a few phrases and a hit on the enter key :P
It stopped in 11,700 years ago
It has the strongest winds in the solar system
Its orbit was used to predict the existence of another planet
It is most well-known for its rings
It has a giant storm three times the width of Earth.
