Answer:
A. Hard
D. 10 days to 8 weeks
D. 5-7 days
A. 10-15 days
Step-by-step explanation:
By the end of the 2nd trimester, the baby's skeleton is hard. This means that the bones have developed to a point where they can be seen on an X-ray.
The baby is called an embryo from 10 days to 8 weeks after fertilization. During this time, the embryo is undergoing critical development of its major organs and structures.
The blastula or blastocyst stage occurs from 5-7 days after fertilization. This stage is characterized by the formation of a fluid-filled cavity called the blastocoel, which will eventually become the embryo's digestive system.
The morula stage occurs from 0-4 days after fertilization and is characterized by a solid ball of cells that will eventually develop into the blastula.
The placenta begins to form around 10-15 days after fertilization. This structure serves as a vital connection between the mother and developing embryo/fetus, providing nutrients and oxygen while removing waste products.