The Following Questions Refer to the Description Below

The following questions refer to the description below.
While on an intersession course in tropical ecology, Kris pulls a large, snakelike organism from a burrow (the class was granted a collecting permit) . The 1-m-long organism has smooth skin, which appears to be segmented. It has two tiny eyes that are hard to see because they seem to be covered by skin. Kris brings it back to the lab at the field station, where it is a source of puzzlement to the class. Kris says that it is a giant oligochaete worm; Shaun suggests it is a legless amphibian; Kelly proposes it belongs to a snake species that is purely fossorial (lives in a burrow) .
-Which of the following structures are possessed only by birds?

A) enlarged pectoral muscles and heavy bones
B) a four-chambered heart
C) feathers and keeled sternum
D) a short tail and scales
E) a large brain and endothermy