which device restricts current flow to a single direction?\na filter\nb diode\nc resistor\nd capacitor

Brief Explanations:

A diode is an electronic component that allows current to flow in one - direction only due to its p - n junction structure. Filters are used to remove certain frequencies, resistors limit the flow of current but not in a directional sense, and capacitors store and release electrical energy.

Answer:

B. diode