Directions: In the following questions, the sentences have been given in Active/Passive voice. From the given alternatives, choose the one which best expresses the given sentence in Passive/Active voice. 

Q:

The beavers have built a perfect dam across the stream  

• 1
  A perfect dam had been built by the beavers across the stream.
• 2
  A perfect dam has been built by the beavers across the stream.
• 3
  A perfect dam have been built by the beavers across the stream.
• 4
  A perfect dam was being built by the beavers across the stream