three
Ozone (O3) is a triatomic, molecule, consisting of three oxygen atoms. Ozone in the upper atmosphere protects living organisms by preventing damaging ultraviolet light from reaching the Earth's surface. O3 is the formula for ozone. It has three oxygen atoms.
Hope this helps:)
1. d
2. b
3. c
4. a
i took this same quiz a while back
Mutagen is an environmental agent that changes the DNA.