Question

The____________ produced by photosynthesis was toxic to many early organisms.

a.Carbon
b.Carbon Dioxide
c.Hydrogen
d.Oxygen

Answer 1

D.Oxygen

Step-by-step explanation:

Oxygen was proven to be fatal to the most common type of organisms present on the Earth at the time.

Answer 2

I am pretty sure it was Oxygen.

Step-by-step explanation:

2 billion years ago, when earth was supposedly formed, the atmosphere had slowly been altered by the gradual addition of oxygen, which proved to be fatal to the most common type of organism present on Earth at the time. {Sorry if it isn't correct.}