After a mother bird lays eggs, she must warm them till they hatch. What is the time from laying an egg to the hatching of the egg called?

The correct option is B.

Incubation period

• The incubation period is the time needed for any particular process of development to take place. For example, the length of time for birds eggs to hatch is the incubation period.
• For an egg to develop normally, it must be exposed for a considerable length of time to an ideal temperature. Indeed, the ideal incubation temperature for many birds' eggs is about human body temperature, 98.6 degrees F.
• Almost all birds create the required temperature by sitting on the eggs and incubating them, often transferring heat via a temporarily bare area of abdominal skin.