Select the correct passive form of the given sentence.
My grandfather built this water-tank in 1950.
1
This water-tank has been built by my grandfather in 1950.
2
This water-tank was built by my grandfather in 1950.
3
This water-tank was being built by my grandfather in 1950.
4
My grandfather had been building this water-tank in 1950.
5
Not Attempted