Detailed Explanation:

Answer: Option 4 — 1 and 3

Among the given animals, hedgehogs and pangolins roll up into a tight ball as a defensive mechanism to protect their vulnerable parts from predators. Hedgehogs use their sharp spines, while pangolins use their tough keratin scales for protection. Marmots, on the other hand, do not roll up; they rely on burrows and alarm calls to avoid predators.

✅ Hedgehog – Correct: Rolls into a tight ball with spines covering vulnerable soft belly parts when threatened.
❌ Marmot – Incorrect: Does not roll up; uses burrows and vocal warning calls as primary defense against predators.
✅ Pangolin – Correct: Rolls into a protective ball, using overlapping keratin scales as armor to shield vulnerable underside.

📝 Short Notes: Defensive Mechanisms in Animals

• Hedgehog: Small spiny mammals found in Europe, Asia, and Africa; covered with about 5,000-7,000 spines made of keratin; rolls into a ball when threatened, making it difficult for predators to attack.
• Pangolin: Only mammal covered in scales; found in Asia and Africa; scales made of keratin (same material as human nails); listed as critically endangered due to illegal wildlife trade; all eight species protected under CITES.
• Marmot: Large ground squirrels found in mountainous areas; social animals living in burrows; use sentinel behavior where one individual watches for predators while others forage; emit high-pitched whistles as alarm calls.
• Other Rolling Animals: Armadillos (three-banded armadillo can roll completely), pill millipedes, pill bugs (woodlice), and some species of armored caterpillars also use rolling as defense.
• Types of Defense Mechanisms: Physical barriers (spines, scales, shells), camouflage, warning coloration, chemical defense (toxins), behavioral (fleeing, freezing, rolling), and group defense.