What is responsible for keeping the percentage of atmospheric oxygen at a relieve constant rate?

 Green plants

Explanation:

The constant  process of photosynthesis which  mopped cabondioixide from the atmosphere  (and the activities of phytoplanktons ) and replace this with Oxygen through photolysis of water, and   is the main driving force that keep the percentages of atmospheric oxygen relatively constant at 20.95%

Additionally the constant release of Carbon dioxide  by animals, and man, as by product of cellular respiration, and the intake of Oxygen  ensured  constant maintenance of continuous  cycle of oxygen for relative constant percentage.

kelp are large brown algae that live in cool, relatively shallow waters close to the shore. they grow in dense groupings much like a forest on land. these underwater towers of kelp provide food and shelter for thousands of fish, invertebrates, and marine mammal species.

e) all of the above