A scientist observes several different fossils in a rock layer. Based on this observation, which is
the best conclusion?
A. The fossils are composed of lava that cooled
around several organisms.
B. The fossils formed about the same time as the
rock layer in which they were found.
C. The fossils formed after heat and pressure
changed the type of rock in the rock layer.
D. The fossils are composed of the same material
as the organisms from which they formed.

A scientist observes several different fossils in a

rock layer. Based on this observation, which is

the best conclusion?

A. The fossils are composed of lava that cooled

A. The fossils are composed of lava that cooledaround several organisms.

B. The fossils formed about the same time as the rock layer in which they were found.

That's the right answer but you can choose one.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.