If (x+3)(x-5) < 0, which of the following must be true?

✓ Correct Answer: Option C

The product of two terms is negative when one term is positive and the other is negative. This occurs when x+3 > 0 and x-5 < 0 (x > -3 and x < 5) or x+3 < 0 and x-5 > 0 (x < -3 and x > 5, which is impossible). Thus, -3 < x < 5.