Which pairs of quantities are directly proportional under the stated conditions? Select all that apply.

Բացատրություն

At a fixed price per kilogram, cost is a constant multiple of mass, and a square's perimeter is four times its side length, so both relationships pass through zero. Age and height do not maintain one fixed ratio, while a rental with an initial charge is the closest false candidate because its constant daily rate is offset by a nonzero fee.