Explanation:
Semi-controlled devices are electronic devices that have one or more controlled terminals and one or more uncontrolled terminals. These devices are used in various applications such as power electronics, motor control, and power supply circuits.

Options:
a) Bidirectional phase controlled thyristor
b) MOSFET
c) Static induction thyristor
d) Fast switching asymmetrical thyristor

Answer:
The correct answer is option 'B' - MOSFET.

Explanation:
A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a type of field-effect transistor that is widely used in electronic devices and circuits. It belongs to the category of controlled devices rather than semi-controlled devices.

Controlled devices vs Semi-controlled devices:
- Controlled devices: These devices have one or more controlled terminals, where the flow of current or voltage can be controlled by an external input signal. Examples of controlled devices include transistors, MOSFETs, and IGBTs.
- Semi-controlled devices: These devices have one or more controlled terminals and one or more uncontrolled terminals. The flow of current or voltage is controlled through the controlled terminals, but the uncontrolled terminals do not have direct control. Examples of semi-controlled devices include thyristors and triacs.

Explanation of other options:
a) Bidirectional phase controlled thyristor: This is a type of thyristor that can control the flow of current in both directions. It is a semi-controlled device.
c) Static induction thyristor: This is a type of thyristor that utilizes static induction effect for its operation. It is a semi-controlled device.
d) Fast switching asymmetrical thyristor: This is a type of thyristor that is designed for fast switching applications. It is a semi-controlled device.

Conclusion:
Among the given options, the MOSFET does not belong to the category of semi-controlled devices. It is a controlled device commonly used in various electronic circuits and systems.