The D. ALLANTOIS is the part of the amniotic egg that collects the metabolic waste produced by the embryo.
An amniotic egg has the following parts.
eggshell - protects the embryo from predators and keeps it from drying out
chorion - beneath the egg shell, allows oxygen to enter, carbon dioxide to exit, and retains water in the egg
amnion - an amnioti fluid fill sac surrounding the embryo, serve as protection and cusion as well as saltwater reservoir
yolk sac - provides protein and fat enriched nutrients from the yolk trasported to the embryo via blood vessels connected to the embryo's gut
allantois - collects metabolic waste excreted by the developing embryo