Rectifiers are used to convert
(A) Direct current to alternating current
(B) Alternating current to direct current
(C) High voltage to low voltage
(D) Low voltage to high voltage

Hint:A power inverter converts the direct electrical signal to alternating electrical signals. A rectifier converts alternating electrical signals to direct electrical signals.
A transformer can change the voltage.

Complete step by step answer:
The alternating electrical signal means the direction of the electrical signal or current changes with a fixed time or periodically. In contrast, the direct current does not change the direction of the current flow.A rectifier is an electrical device.It can convert the alternating electrical signal into the direct electrical signal by half-wave and full-wave rectification.
A rectifier circuit can work as a single-phase or multiphase.Single-phase rectifiers are used in low power supplies. Multiphase rectifiers are used in high power supplies. Now In the case of an inverter, we can convert the DC(direct current) into the alternating current. Batteries and fuel cells are the typical examples of Inverter source.Similarly, a transformer can change the voltage. A Step-up transformer is used to generate the high voltage from the low voltage.
Step down transformers are used to create low voltage to the high voltage.
So the correct answer is option (B) Alternating to direct current.

Note:Rectifiers can be found in DC power supplies.It is also used in high voltage transformer.Rectifiers serve as radio signal detectors.