Choose the statements that are correct with respect to continuous culture systems:
(A) In a simple stirred tank bioreactor, stirring happens through sparging of air bubbles
(B) A bioreactor has an agitator system, oxygen delivery system, and foam control system
(C) Sampling ports provide vents to withdraw small volumes of culture periodically
(D) Culturing in bioreactors is classified as downstream processing
Choose the correct answer from the options given below: