A sentence has been given in Active/Passive Voice. Out of the four given alternatives, select the one which best expresses the same sentence in Passive/Active Voice.
Pipe A can empty a filled tank in 28 hours while Pipe B can fill the same tank, when empty in 35 hrs. If alternatively Pipes A and B are turned on for an hour each time, starting when the tank is full, how long will it take to empty the tank?
High-efficiency particulate air (HEPA), also known as high-efficiency particulate absorbing and high-efficiency particulate arrestance, is an efficiency standard of air filter.