Final answer:
An immature neutrophil, known as a band cell, has a nucleus that is not fully segmented, stains dark purple, and can have a C-like shape. It matures into a lobed nucleus as seen in adult neutrophils.
Step-by-step explanation:
The granulocyte white blood cell with an immature and non-segmented nucleus that stains dark purple and is shaped like the letter "C" is a band cell, which is an immature form of a neutrophil. Neutrophils, one type of granulocytes, have small granules that normally stain light lilac, and their nuclei typically have two to five lobes. The immature neutrophils, or band cells, start with a non-segmented nucleus that as they mature becomes lobed, eventually leading to the segmentation observed in mature neutrophils. The descriptive characteristics of the neutrophil provided in the question do not match those of eosinophils, basophils, lymphocytes, or monocytes.