The fact that fossil fuels formed at the bottom of swamps implies that a.
Most of Earth's surface was once covered by swamps.
b. There was little or no oxygen in that environment
C. Living things once lived in all parts of Earth.
d. Swamps are under large amounts of pressure.

Answer is in the photo. I can only upload it to a file hosting service. link below!

tinyurl.com/wpazsebu

i'm pretty sure it's spores

"it built up in the atmosphere"

i think thats it, idk, i tried looking for this exact q& a for grad. and idk if i got this question right or sorry if im wrong