The correct answer is: B. Silicon carbide
Voltage dependent resistors (VDRs) are also known as varistors or voltage-dependent varistors. They are nonlinear resistors whose resistance decreases with increasing applied voltage. VDRs are typically made from silicon carbide (SiC), which is a semiconductor material. SiC has a wide bandgap, which means that it is not easily ionized by an electric field. This makes SiC a good material for VDRs, as it allows them to withstand high voltages without breaking down.
Charcoal is a form of carbon that is produced by the incomplete combustion of organic materials. It is a good conductor of electricity, but it is not typically used to make VDRs.
Nichrome is a nickel-chromium alloy that is commonly used to make heating elements. It is a good conductor of electricity, but it is not typically used to make VDRs.
Graphite is a form of carbon that is made up of layers of carbon atoms. It is a good conductor of electricity, but it is not typically used to make VDRs.
In conclusion, the correct answer is: B. Silicon carbide.