Refer to the following passage to answer the following questions. Oxygen is a waste product of photosynthesis that reacts readily with iron. Three billion years ago atmospheric oxygen concentration increased and free iron in ocean water decreased as a result of photosynthetic prokaryotes. The decrease in free iron in the ocean was followed by the evolution of photosynthetic eukaryotes. Oxygen concentration continued to increase. The increased oxygen further depleted the remaining free iron in the ocean and led to increased atmospheric oxygen and the emergence of land plants.

The relationship between the evolution of life and the composition of our atmosphere has resulted in many changes to our planet. One of the first major changes was the addition of oxygen due to photosynthetic activity of photosynthetic prokaryotes. What would you expect to find in large amounts in rock bands that formed during this time period?

a
Bands of fossilized dinosaurs
b
Bands of fossilized plants
c
Bands of iron oxides
d
Bands of solid iron