Answer:
D. principle of original horizontality
Step-by-step explanation:
When you come upon a series of folded sedimentary strata in the field, the principle of original horizontality can be use to determine that they must have been disturbed after their deposition.
The principle of original horizontality which was proposed in the 17th century by Nicholas Steno states that layers of sediment are originally deposited horizontally under the action of gravity, and thus, any disturbance in the consistency of these layers is an indication that it must have been disturbed.