1 Switch is equivalent to 1 bit Cz Switch store either on or off value like a bit can be 0 or 1.
So total 12 bits are there(cz there 12 switches)
Make 3 group of 12 bit . Means each group contain 4 bit.
(_ _ _ _) (_ _ _ _) (_ _ _ _)
G1. G2. G3
Here in any group max 10 numbers can be stored Cz BCD numbers we have to store.
So 10*10*10 different BCD numbers can be stored in this 12 Switches. So Ans is option D) 10^3