Final answer:
The Wood Duck has a green head and a chestnut lower back and breast area separated by a white ring.
Step-by-step explanation:
The duck with a green head and a chestnut lower back and breast area separated by a white ring is the Wood Duck (C). The male Wood Duck has a striking appearance with its colorful plumage. It has a green crested head, chestnut-colored lower back and breast area, and a white ring around its neck.
The Mallard (A) has a green head too, but it does not have the distinctive chestnut lower back and breast area separated by a white ring. The Northern Pintail (B) and Canvasback (D) also do not have the same coloration as described.