Select the option that expresses the given sentence in passive voice.
The architects have built a sturdy tower in the middle of Melbourne City.
1
A sturdy tower had been built by the architects in the middle of Melbourne City.
2
A sturdy tower has been built by the architects in the middle of Melbourne City.
3
A sturdy tower have been built by the architects in the middle of Melbourne City.
4
A sturdy tower was being built by the architects in the middle of Melbourne City.