Question

The diagram below shows two processes, P and Q, in the carbon cycle.

The picture shows a rectangular box labeled 'Carbon in atmosphere.' Below the box there is an arrow labeled P pointing downwards. Below the arrow P there is a rectangular box labeled 'Ocean.' There is an arrow pointing downwards, below the box labeled 'Ocean.' Below the arrow there is a rectangular box labeled 'Carbon in limestone.' An arrow labeled Q points from 'Carbon in limestone' towards 'Carbon in atmosphere.'

Which of these statements best describes the processes P and Q?