Transistor

I know LEDs can only be used with DC Currnt but can Transistors be used with AC and DC or just DC Current?
Thans.

It depends what you mean by 'used'.
A bipolar junction transistor can pass collector current in one direction only (i.e DC), but if correctly biased the transistor can be used to amplify an AC signal by varying the base-emitter voltage and hence modulating the collector current.
A MOSFET, when turned on by a suitable gate-source voltage, can pass AC current through its drain-source path.

To perhaps clarify, when a transistor (BJT or FET) is used to amplify an AC signal, it is biased from a DC source.