What is the disadvantage of using a full wave rectifier?

The main disadvantage of a bridge rectifier is that it needs four diodes, two of which conduct in alternate half-cycles. Because of this the total voltage drop in diodes becomes double of that in case of centre-tap rectifier, losses are increased and rectification efficiency is somewhat reduced. This poses a problem when low voltages are required. Another disadvantage of bridge rectifier is that the load resistor R

Land the supply source have no common point which may be earthed.