The period of inactivity seen in some animals during long period of heat or drought is

Analyze the question: The question asks for the term for a period of inactivity in animals during a long period of heat or drought. The key words are "inactivity" and "heat/drought."

Explain the concepts:

• Migration: Seasonal movement of animals from one place to another, so it is not inactivity.
• Aestivation: A state of dormancy or inactivity during hot, dry conditions (summer sleep). The animal lowers its metabolic rate to survive heat and water shortage.
• Hibernation: A state of dormancy during cold weather (winter sleep).
• Adaptation: Any structural, physiological, or behavioural feature that helps an organism survive in its environment. It is a general term, not specific to inactivity.

Solution:

1. The inactivity is triggered by heat or drought, not cold. This rules out hibernation (C).
2. The animals stay in place and become inactive, so it is not migration (A).
3. "Adaptation" is too broad and does not describe a specific period of dormancy (D).
4. The term for dormancy during hot, dry spells is aestivation.

Examples: African lungfish (Protopterus) burrow into mud and aestivate during the dry season, and snails seal their shells during drought.

Tip: Link the first letters: Aestivation = Arid/Air-hot (summer), Hibernation = Harmattan/High cold (winter). Another way: "Hibernate in Hibernal (winter) cold; Aestivate in Aestival (summer) heat."