What domain makes sense for the function in this context? Please Hurry

A. All positive numbers
B.
C. All real numbers
D.

John bought 5 lemons and used 2 of them for a salad how much did he use for.a salad . he used % of the lemons.

Kayla and alberto are selling fruit for a school fundraiser. customers can buy small boxes of grapefruit and large boxes of grapefruit. kayla sold 3 small boxes of grapefruit and 1 large box of grapefruit for a total of $65. alberto sold 1 small box of grapefruit and 1 large box of grapefruit for a total of $55. what is the cost each of one small box of grapefruit and one large box of grapefruit?

Can someone answer this question for me