What will you call the amount of money borrowed or invested?
Correct option is D. principal
The amount of money borrowed or invested is called as $$Principal.$$
When you first take out a loan, the principal is the original amount you borrowed.
As you pay toward that debt, the principal becomes the outstanding balance on the loan, not including interest and any fees accrued.
Depending on the type of loan you have, your payments will include money for both principal and interest.