A dephlegmator is a

ANS:C - partial condenser

A dephlegmator is a partial condenser. A dephlegmator is a type of heat exchanger used in distillation processes to partially condense vapor. It consists of a series of tubes or plates through which the vapor passes, and cold liquid or reflux flows countercurrently. The dephlegmator helps to separate the vapor into its components by condensing a portion of the vapor, while allowing the remaining vapor to pass through. This partial condensation helps to increase the purity of the desired product by removing lighter components from the vapor mixture. So, the correct option is: partial condenser.