Static Induction Thyristor:
A static induction thyristor (SIT) is a type of semiconductor device that is used for power control applications. It is a three-terminal device that consists of an anode, a cathode, and a gate. The SIT is designed to handle large amounts of power and can switch between on and off states to control the flow of current.

Majority Carrier Device:
In a semiconductor device, whether it is a majority or minority carrier device depends on the type of charge carriers that contribute most to the current flow. In a majority carrier device, the majority charge carriers (either electrons or holes) are responsible for the current conduction.

Minority Carrier Device:
In a minority carrier device, the minority charge carriers, which are present in smaller quantities, dominate the current conduction. The minority carriers typically have a shorter lifetime and mobility compared to the majority carriers.

Explanation:
The correct answer is option 'B' - a static induction thyristor is a minority carrier device. This means that the minority charge carriers (either electrons or holes) are responsible for the current conduction in the SIT.

The operation of a static induction thyristor is based on the control of minority carrier injection at the gate region. When a positive voltage is applied to the gate terminal, it creates a channel between the anode and cathode, allowing the minority carriers to flow and turn on the device. Conversely, when a negative voltage is applied to the gate terminal, the channel is blocked, and the device turns off.

Since the device relies on the control of minority carriers, it is classified as a minority carrier device. This is different from conventional thyristors, such as silicon-controlled rectifiers (SCRs), which are majority carrier devices.

Conclusion:
In summary, a static induction thyristor is a minority carrier device. It operates by controlling the injection of minority carriers at the gate region to turn the device on and off. Understanding the type of charge carriers involved in the conduction of a semiconductor device is crucial for its proper operation and analysis.