Final answer:
Layers of igneous and metamorphic rock typically lack evidence of living organisms, unlike sedimentary rocks. The earliest evidence for life is in the form of fossilized microbial mats found in 3.5 billion-year-old rocks, specifically stromatolites. Banded iron formations suggest the rise of oxygen production by photosynthetic organisms in Earth's early history.
Step-by-step explanation:
The two layers of rock where you do not see any evidence of living organisms are likely igneous and metamorphic rocks, as opposed to sedimentary rocks which are typically where fossils are found. The oldest fossil evidence for life includes microbial mats, indicating that the type of evidence for life found in a 3.5 billion-year-old rock was likely fossilized microbial mats that superficially resemble the living microbial mats of today, as seen in option (c).
These mats are formed by colonies of single-celled microbes, such as cyanobacteria, that trap sediment and create layered structures known as stromatolites, which are profound in the rock record. The appearance of banded iron formations also provides key insights into early Earth conditions, suggesting that photosynthetic organisms emerged and produced oxygen, which reacted with iron in the water to form precipitates of hematite and magnetite.