Final answer:
The principle that deals with the original orientation of a rock layer formed by sediments settling from a fluid is original horizontality.
Step-by-step explanation:
The correct geological principle that deals with the original orientation of a rock layer formed by sediments settling from a fluid is original horizontality.
Original horizontality states that layers of sediment are originally deposited horizontally. This means that any tilting or folding of the rock occurred after it was deposited. The principle of original horizontality helps geologists understand the relative ages of rock layers and interpret the geological history of an area.
For example, if a series of horizontal sedimentary rock layers are found, and a fault cuts through these layers, it can be concluded that the fault is younger than the sedimentary rocks because the rocks had to exist first to be faulted.