first, let's take one dry cell (or u call it one battery, which is incorrect btw) to be 1 V
&
if the dry cells point in the same direction, we add, &
if the dry cells point in the different directions, we subtract

option (1)
there would be 3 dry cells in the same direction. and 1 dry cell in the opposite direction
so we add 1+1+1 = 3 V &
subtract 1 V => 3 - 1 = 2 V
hence the bulb would lit up.
option (1) is not the ans.


option (2)
there would be 2 dry cells in the same direction. and 2 dry cells in the opposite direction
so we add 1+1 = 2 V &
subtract 2 V => 2 - 2 = 0 V
hence the bulb would NOT lit up.
option (2) is the ans.

& this applies the same to (3) & (4)
u can figure them out yourself.

Thanks snell.
They don teach this method in sch but it makes sense!