Leukocytosis Commonly Refers to an Increase in Peripheral Blood White $\mu$

Leukocytosis commonly refers to an increase in peripheral blood white blood cell (WBC) counts of greater than what value?

A) 5000 cells/ $\mu$ L
B) 1000 cells/ $\mu$ L
C) 10,000 cells/ $\mu$ L
D) 8000 cells/ $\mu$ L
E) 4000 cells/ $\mu$ L