Which best explains how photosynthesis is helpful to humans? It reduces the amount of harmful rays released by the sun. It increases the levels of carbon dioxide in the air. It provides oxygen for humans to breathe. It produces proteins, which humans can eat.

I believe that the answer is c

Explanation: photosynthesis gives us oxygen to breath therefore it is helpful to humans

it provides oxygen for the human to breathe

Explanation:

i believe that it is a exoplanet

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.