The developing embryo is attached to the mother’s uterus by

Step 1: Analyze the question The question asks which structure attaches the developing embryo to the mother's uterus. The key word is "attached to the mother's uterus."

Step 2: Review the concepts

• Amnion: a membrane that encloses the amniotic fluid and cushions the embryo. It does not attach it to the uterus.
• Blood vessels: these carry materials, but they are not the attachment structure itself.
• Placenta: a disc-shaped organ that develops from both embryonic tissue (the chorion) and the mother's uterine lining. It embeds in the uterine wall, so it is the structure that physically attaches the embryo/foetus to the uterus. It also allows exchange of oxygen, nutrients, and wastes between mother and foetus.
• Umbilical cord: connects the foetus to the placenta, not directly to the uterus.
• Uterine cavity: the space inside the uterus, not an attaching structure.

Step 3: Solve The chain of attachment is: embryo → umbilical cord → placenta → uterine wall. The part that is actually fixed to the uterus is the placenta. The umbilical cord links the embryo to the placenta, not to the uterus itself.

Answer: C. placenta

Exam tip: Remember the chain "Cord connects the baby to the placenta; the placenta connects to the uterus." If a question says "attached to the uterus," think placenta. If it says "connects the foetus to the placenta," think umbilical cord.