Based on the fact that the $19,000 was secured as a loan by Nadia, it is considered the A. principal.
The principal in relation to a loan refers to the original amount that was borrowed.
In this case, the original amount borrowed as a loan was the $19,000 that Nadia needed to complete the amount she needed to get a car.
In conclusion, option A is correct.
Find out more on the principal at https://brainly.com/question/25545513.