D. unique in its appearance. Index fossils must have a unique form that is easy to identify without special equipment. Geologists make maps in the field as they gather data and specimens. If the index fossil is easy to identify without the use of a microscope or laboratory equipment, the field work can process more quickly.
People don't have feathers so D is not an option. Alliteration is the repetition of the same beginning sound in a group of words so that also is not an option. Simile uses like or as - not an option. Metaphor is a comparison of two different things, hope to a bird (thing with feathers). B is correct.
