A student mapped his city's geology by drawing a cross section of what he sees when looking at a plateau with exposed bedrock. After collecting samples from the different types of rock, he sent in his samples for radiometric dating to get absolute ages. The samples came back, but all the labels fell off inside the box. Fortunately, the student knows where each sample came from in his drawing. Using the relative age dating technique, he can determine which label matches which rock. According to the law of superpositioning, sedimentary layers are horizontally deposited in a sequence where older rocks are typically on the bottom and younger rocks are on top. According to the principle of cross-cutting relationships, the rock feature that cuts through the other is younger than the one it is cutting through. If a layer affects another layer by heating it, the affected layer is older.

On the basis of the sample data presented, sample C formed approximately:

options:

0.5 million years ago

2 million years ago

40 million years ago

100 million years ago