How many days is used for incubation of an egg to release chick

Analyze the question: The question asks for the incubation period of a hen's egg, meaning the number of days from when the egg starts being incubated (by the hen or an incubator) until the chick hatches.

Concept: Incubation is the process of keeping fertilized eggs warm so the embryo can develop. The length differs between birds:

| Bird | Incubation period | |------|------------------| | Chicken (hen) | 21 days | | Duck | 28 days | | Turkey | 28 days | | Guinea fowl | 26-28 days | | Goose | 28-35 days | | Quail | 17-18 days |

Solution:

1. The question says "chick", which points to the domestic fowl (chicken).
2. A fertilized hen's egg needs a steady temperature of about 37.5-39°C (99-102°F) to develop.
3. Over this time the embryo develops, feeding on the yolk, and then pips (breaks) the shell.
4. Hatching occurs on day 21.

Answer: A. 21

Exam tip: Remember "chicken = 3 weeks" (3 × 7 = 21). Ducks and turkeys take 4 weeks (28 days). If a JAMB question says "chick" or "hen" without naming another bird, go for 21 days.