D hope that helps you out
Answer: The nervous system
Explanation:
The first part of the embryo to develop is the neural tube, which will become the spinal cord and brain. As the nervous system starts to develop, the tiny heart starts to pump blood, and other parts of the body—such as the digestive tract and backbone—begin to emerge.
Your mouth, nose, throat, sinuses and lungs are lined with mucus membranes. These membranes contain mucus glands that produce - surprise - mucus. Mucus-producing membranes line specific passages in your body, like the respiratory and digestive tracts, for protection and support.
Answer:
Once your body starts producing the pregnancy hormone human chorionic gonadotrophin (hCG), your periods will stop. However, you may be pregnant and have light bleeding at about the time that your period would have been due.
Explanation: