Antonym of 'rapid'.

**The reasoning** An **antonym** is a word that means the *opposite* of another word. Think of it like hot vs. cold, big vs. small. "Rapid" means *fast* or *happening quickly*. So we need a word that means the opposite — something that happens at a low speed or takes a long time. **Slow** is the direct opposite of rapid. When something is slow, it moves or happens at a reduced pace, which is exactly contrary to being rapid. **Why the wrong options tempt you** - **Quick (A)** — This is a *synonym* (similar word), not an antonym! Both "rapid" and "quick" mean fast. Don't confuse the two. - **Smart (C)** — This describes intelligence, not speed. Completely unrelated to rapid. - **Loud (D)** — This describes volume/sound, not speed. Another unrelated concept. The trick here is spotting that "quick" *sounds* like it could be right because it's related to speed — but it's actually the *same* meaning, not the opposite. **Quick takeaway** Antonym = opposite meaning; synonym = similar meaning. Rapid ↔ Slow, just like fast ↔ slow.