Litmus paper turns _____ in an acid.

## The reasoning Think of litmus paper as a **color-coded messenger** that tells you whether a solution is acidic or basic. This is based on a simple chemical principle: **acid-base indicators change color depending on pH**. Litmus is a natural dye extracted from lichen. In an **acidic solution** (like lemon juice, vinegar, or dilute HCl), litmus paper turns **red**. In a **basic solution** (like soap water or NaOH), it turns **blue**. The memory trick: **"Acids Are Red"** — both start with 'A'. Simple! ## Why the wrong options tempt you **Blue (A)** — This is what happens in a *base*, not an acid. Students often confuse the two directions. **Green (C) & Black (D)** — These aren't litmus colors at all. They're just distractors playing on uncertainty. Litmus only goes between red and blue. ## Quick takeaway **Acids turn litmus RED, bases turn it BLUE** — remember "Acids Are Red" and you'll never mix them up again!