Julian's coworkers often come to him for information about how their company handled disgruntled customers in the past since he has worked at the company for 25 years. The information he provides is not written down, but it is invaluable in helping his coworkers in making decisions about how to deal with difficult customers. Julian's information is an example of ____ knowledge.
a. explicit
b. descriptive
c. vigilant
d. tacit