Answer: c) 16 bits
Step-by-step explanation: Protected mode is the mode which works when the phase of CPU of an operating system which allows to use the virtual memory of the system. It is different from the real world mode and has the codes of 32 bit or 16 bits. For the protected mode ,the size the selector register becomes of 16 bits.When you enter any 16 bit value , it get into the selector register.