Answer:
Fourth and Fifth month
Step-by-step explanation:
The fourth and fifth months formed the major part of the second trimester, and it is characterized by the growth of the brain and central nervous system which shows more alertness and developed faster in a way that appears similar to that of a new baby.
Also, this fourth and fifth month is characterized by growth in other parts of the unborn baby such as an increase in heartbeat, fingernails, hair, eyelashes, and toenails.