The correct answer is: B. Vgs greater than Vt.
The linear region is the region of operation of a MOSFET where the drain current is proportional to the gate-source voltage. This region is typically used for amplification and linear applications.
The threshold voltage, Vt, is the minimum gate-source voltage required to turn on a MOSFET. When Vgs is greater than Vt, the MOSFET will start to conduct current. The amount of current that flows through the MOSFET is proportional to the difference between Vgs and Vt.
When Vgs is much greater than Vt, the MOSFET will be in the saturation region. In this region, the drain current is no longer proportional to Vgs. The saturation region is typically used for power switching applications.
The following figure shows the typical I-V characteristics of a MOSFET. The linear region is the region between the threshold voltage and the saturation voltage.
The options A, C, and D are incorrect because they do not describe the condition for the linear region.