Answer:
A. A placenta
Explanation:
The placenta is an organ that can be found in the female mammal. It develops when the foetus is developing. The placenta is needed during pregnancy, that's why it doesn't grow in male.
In human (female), when the pregnancy gets to 8 weeks, the placenta develops tiny hairlike projections.
Blood vessels from the embryo, which pass through the umbilical cord to the placenta, develop in the villi.
This will then extend into the wall of the uterus
