Underlying blood vessels give nails a pinkish appearance. near the nail root, however, the blood vessels lie deeper in the skin, resulting in a pale crescent, called the:

lunula

Explanation:

The lunula is crescent-shaped whitish colored area of bed of the nail.

It is present at end of the nail.The lunula is not actually white in color but only appears white when it is seen through nail.  

Outlining nail matrix, lunula is extremely delicate part of structure of the nail. If one damages lunula, nail will be deformed permanently.  

It appears whitish in color because of the  stratum basale obscures that underlies blood vessels.

the correct answer is option b

behavioral response need communication and thus co-ordination at several levels such as interaction among cells, organ system and the entire organism.

behavioral response produces both internal and environmental stimulus.