Plz help
A prehistoric clamshell is buried by sediment on the seafloor. Over time, the sediment turns to rock, and the clamshell dissolves away. This leaves behind a cavity in the rock that is shaped like the clamshell.


What kind of fossil is this clamshell-shaped cavity?

A

a mold

B

a carbonized fossil

C

a petrified fossil

D

a cast


The rock and fossil record shows that

A

both gradual and sudden changes have occurred during Earth's history.

B

all of the changes during Earth's history have been slow and gradual.

C

the Earth has not changed very much over the course of its history.

D

all of the changes during Earth's history have been very sudden.