Oxygen was Discovered by:
Option 3 is the right answer.
Oxygen was “discovered” by a number of scientists over a fairly brief time period. First discovery is normally credited to the Swedish scientist Carl Wilhelm Scheele in 1772. He called his discovery “fire-air” because it supported combustion.
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetallic element and oxidizing agent that readily forms compounds (notably oxides) with most elements. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium. At STP, two atoms of the element bind to form dioxygen, a diatomic gas that is colorless, odorless, and tasteless