Adele is buying a sport utility vehicle. She is trying to choose among a variety of options.

Brand: Brand A or Brand B

Transmission: 4-speed standard, 5-speed standard, or automatic

Bumper: steel, vinyl, or 2x4 boards

Roof: hard top or convertible top

Adele calculates that she has 2 + 3 + 3 + 2, or a total of 10, possible vehicle choices

What is Adele’s error?
She should have added only the transmission and bumper choices.
She should have added only the brand and roof choices.
She should have multiplied the total of all the choices.
She should have multiplied only the brand and roof choices.