Final answer:
Fossils are indeed the preserved remains of bones, teeth, or shells that have undergone a process of mineralization, effectively turning them to stone, which makes the statement 'Fossils are bones and shells turned to stone' true.
Step-by-step explanation:
When discussing fossils, it is important to understand that they are indeed the preserved remains or traces of organisms that lived in the past. This preservation often involves the mineralization of bones, teeth, or shells, effectively turning them to stone. Particularly, bones make good fossils because bone tissue, under the right conditions, will undergo this process of mineralization.
Once living organisms with bones will, after death and the decay of soft tissue, leave behind these hard parts. Given favorable conditions such as the presence of volcanic ash, limestone, or mineralized groundwater, these hard parts can mineralize and thus become fossils. Therefore, the statement that 'Fossils are bones and shells turned to stone' falls in line with the scientific understanding of fossil formation and would be considered true.