What does a %= 5 do to the variable a?

• A. Divides a by 5 and keeps remainder.
• B. Multiplies a by 5.
• C. Sets a to 5 modulo a.
• D. Sets a to a modulo 5.

Answer: (D)

Modulus assignment uses the remainder after division. a %= 5 replaces a with the remainder of a divided by 5, which is the same as a = a % 5. So after this operation, a holds only the part that remains when you divide by 5. For example, if a is 13, a becomes 3; if a is 20, a becomes 0. It doesn’t divide, multiply, or set a to 5 modulo a—it's specifically the remainder of a divided by 5.