Study the following figure and identify (a) and (b).

• A

  (a) is sparged tank bioreactor and (b) is stirred tank bioreactor

• B

  (a) is sparged tank bioreactor and (b) is thermocycler

• C

  (a) is stirred tank bioreactor and (b) is PCR machine 

• D

  (a) is stirred tank bioreactor and (b) is sparged tank bioreactor