Select the correct active form of the given sentence.Mobile toilets were placed by the district administration behind the area where people assembled for army recruitment.

• A. The district administration has placed mobile toilets behind the area where people assembled for army recruitment.
• B. The district administration placed mobile toilets behind the area where people assembled for army recruitment.
• C. The district administration is planning to place mobile toilets behind the area where people will assemble for army recruitment.
• D. The mobile toilets placed district administration behind the area where people assembled for army recruitment.