Among the various models of Delta vacuum cleaners, one cannot accurately predict how effectively a particular model cleans simply by determining how powerful its motor is. The efficiency of dust filtration systems varies significantly, even between models of Delta vacuum cleaners equipped with identically powerful motors. The argument's conclusion is properly drawn if which one of the following is assumed? ['All Delta vacuum cleaners that clean equally effectively have identically powerful motors.', "One cannot accurately assess how effectively any Delta vacuum cleaner cleans without knowing how powerful that vacuum cleaner's motor is.", 'For each Delta vacuum cleaner, the efficiency of its dust filtration system has a significant impact on how effectively it cleans.', 'For any two Delta vacuum cleaners with equally efficient dust filtration systems, the one with the more powerful motor cleans more effectively.']