When was oxygen first produced?

Match the examples to the correct level of organization. 1. system level roses, snakes, puppies 2. organism level roots, stamens, leaves 3. tissue level bone, cartilage, blood 4. organ level heart, veins, arteries

Idon’t know the answer and i’ve been stuck on it for a while now skskskskks

Isotopes of the same element have differ in their