A bacteriophage is a kind of germ that can prey on bacteria. At present, with the development of implantation technology in medical treatment, more and more patients are receiving medical implants such as urinary catheters, heart stents, etc. Because of the risk of bacterial infection, some researchers believe that if the phage is adsorbed on the surface of the implanted material and placed in the patient, the infection caused by the implanted quantity can be avoided. Which of the following is true and can most weaken the above conclusion? ['For patients implanted with medical volume, antibiotics are generally used to prevent bacterial infections.', 'Where there are bacteria, there may be corresponding phages, but the number is different.', 'Bacteriophages can attack disease-causing bacteria, but sometimes there are "predatory" beneficial bacteria.', 'After some phages enter the body, they cannot adapt to the body fluid environment and it is difficult to maintain their activity.']