The correct option is B 7 Ω
The three 3 Ω resistances present in the middle are parallel to one another.
Hence, their effective Resistance Rp can be calculated as:
⇒Rp=3 Ω3=1 Ω.
This 1 Ω is in series with the other 1 Ω and 5 Ω resistors.
Hence, the equivalent resistance becomes 1 Ω+1 Ω+5 Ω=7 Ω.