The main purpose of the passage can be expressed most accurately by which of the following? A. To contrast the manner by which bacteria and viruses infect the human body and cause cellular damage. B. To explain the operations by which viruses use cell machinery to propagate. C. To argue for additional resources to combat drug-resistant bacteria and easily transmissible pathogenic viruses. D. To highlight the good fortune experienced by the human race, in that the HIV pandemic has not been more lethal. E. To compare the relative dangers of two biological threats and judge one of them to be far more important.