Are fossils used to study A how ancient animals behaved, B organisms that once lived, see organisms that live today, or d phylogenic trees

Fossils are used to study B organisms that once lived. Fossils provide evidence of past life forms, allowing scientists to learn about the anatomy, behavior, and ecology of ancient organisms. By studying fossils, researchers can reconstruct the history of life on Earth and understand how different species have evolved over time. Additionally, comparing fossils to living organisms can provide insights into evolutionary relationships and the diversity of life on Earth.