Which of the following is not a principle of relative-age dating?
a. in undisturbed rock layers, the youngest rocks are on the bottom.
b. sediments are deposited in lateral sheets, but their orders often change.
c. if one rock contains pieces of another, the rock containing the pieces is older than the pieces.
d. rock-forming materials are deposited in horizontal layers, though they may be tilted later.

A. In undisturbed rock layers, the youngest rocks are on the bottom.

C. If one rock contains pieces of another, the rock containing the pieces is older than the pieces.

Explanation:

Relative dating is a form of dating rocks in which past events in geologic records are put their proper order without necessarily knowing their absolute ages. There are several principles that helps in relative dating of rocks. These principles are:

Option A and C are false statements of principle of superpositon of strata and principle of inclusion.

A. In undisturbed rock layers, the youngest rocks are on the bottom.

According to the principle of superpositon of strata, "the oldest sedimentary rock layers are usually at the bottom and the youngest on the top".

C. If one rock contains pieces of another, the rock containing the pieces is older than the pieces.

This is a false statement of principle of inclusion, the principle states that "inclusions found in a sedimentary rock are older than the rocks that contains them". Inclusions are fragments or pieces of other rocks that are found in a rock. These inclusion are believed to be older than the rocks they are found in.