Assuming signal C originates from at least a 3.3V power supply, you could use a relay that accepts a 3V3 coil voltagerelay that accepts a 3V3 coil voltage and drive that relay indirectly with signal C.
Example: JQC-3F-03VDC
Another solution could be using a (mosfet) solid-state relay, but check the maximum load current does not exceed the specs. Maybe signal C can drive the LED directly (i.e. with a resistor in series).
Example: VO1400AEF