Question

which fossils are formed by sediments and found in sedimentary rock?
a mold of a fish skeleton and a cast of a clamshell
a cast of a clamshell and a frozen animal
a frozen animal and a piece of petrified wood
a piece of petrified wood and a preserved insect

Explanation:

• Mold and cast fossils: Mold fossils form when an organism is buried in sediment, and the sediment hardens around it. Then the organism decays, leaving a cavity (mold). A cast is formed when the mold is filled with sediment or minerals. These processes occur in sedimentary environments.
• Frozen animals: Frozen animals are not formed by sediments. They are preserved in ice (permafrost, for example) due to cold temperatures, not sedimentary processes.
• Petrified wood: Petrified wood forms through a process of permineralization. Minerals replace the organic material of the wood over time. While it can be found in sedimentary rock, the key process is mineral - replacement rather than simple sediment - based formation like mold and cast.
• Preserved insects: Preserved insects (like in amber) are preserved in tree resin that hardens. This is not a sediment - based formation process.

Answer:

a mold of a fish skeleton and a cast of a clamshell