Question

which statement about how geologists study the ages of rock layers is true?
the law of superposition means that older rocks are on top.
geologists can find the exact age of a rock by looking at its relative position.
the principle of original horizontality provides the basis for the law of superposition.
relative age can be determined by using the concept of unconformity.

Explanation:

The law of superposition has older rocks at the bottom. Relative position gives relative not exact age. The principle of original horizontality and law of superposition are different concepts. Unconformities help in determining relative ages of rock - layers.

Answer:

D. Relative age can be determined by using the concept of unconformity.