The correct answer is: C. many turns of thin wire.
A D.C. shunt relay is a type of relay that uses a shunt resistor to control the flow of current through the coil. The shunt resistor is made of many turns of thin wire, which allows it to have a low resistance and a high current carrying capacity. This makes it ideal for use in D.C. circuits, where the current can be high.
The other options are incorrect because they do not describe the correct type of wire used in a D.C. shunt relay. Option A, few turns of thick wire, would not allow enough current to flow through the coil to activate the relay. Option B, few turns of thin wire, would not have a high enough current carrying capacity to be used in a D.C. circuit. Option D, many turns of thick wire, would have a high resistance and would not allow enough current to flow through the coil to activate the relay.