Identify the correct labeling and its function from the given diagram of a developing fetus.

• A
  $A$ - Chorionic villi $\rightarrow$ Forms placenta
• B
  $B$ - Yolk sac $\rightarrow$ Prevents desiccation of embryo
• C
  $C$ - Umbilical cord $\rightarrow$ Haemopoiesis
• D
  $D$ - Blastocyst $\rightarrow$ Forms the embryo