The Word "Session" When Someone Uses It in Conjunction with the Production

The word "session" when someone uses it in conjunction with the production of a radio commercial refers to the:

A) group of people who are brought together to make the commercial.
B) length of time the final commercial is supposed to last.
C) period of time during which the recording and mixing of sound take place.
D) number of weeks (or months) the commercial is scheduled to be aired.
E) loudness level that is to be used to record the commercial.