The following expression is correct:

Select one:a$.$ The BJT$,$ MOSFET and IGBT require pulse gate signal in order to operateb. The silicon controlled rectifier $($Thyristor$)$ is controlled turn off and uncontrolled turn onc. The GTO and SCR $($Thyristor$)$ require continuous gate signal in order to operated. The GTO, BJT and SCR $($Thyristor$)$ have unidirectional current capability