Question

people of charles darwins time understood that fossils were
unrelated to living
species
preserved remains of
ancient organisms
available for every
organism that ever
lived
evidence for the
evolution of life on
earth

Explanation:

Fossils are defined as the preserved remains (or traces) of ancient organisms. The other options are incorrect: fossils are related to living species (so "unrelated to living species" is wrong), not every organism that ever lived becomes a fossil (so "available for every organism that ever lived" is wrong), and while fossils do provide evidence for evolution, the understanding in Darwin's time about what fossils are (their basic definition) centered on being preserved remains of ancient organisms.

Answer:

B. preserved remains of ancient organisms (assuming the purple option is labeled B; if the original labels were different, adjust the identifier but the text is "preserved remains of ancient organisms")