What can scientists learn from the rate at which radioactive elements decay?

A. a rock's absolute age*
B. the relative age of rock layers
C. where one soil horizon ends and the next begins
D. the difference between molds and casts.

The relative age of a rock is
A, its age based on how much carbon-14 it contains
B. its age compared with the ages of other rocks *
C. less than the age of the fossils it contains
D. the number of years since it formed

After six half-lives, what percentage of a radioactive sample will remain?

A. 0%-1%
B. 1%-3%*
C. 3%-6%
D. 6%-10%

Earth's oceans, atmosphere, and continents began to form during the first several hundred years of Precambrian time.

A. True*
B. False

A mold forms when minerals replace all or part of an organism.

A. True
B. False*