The word "bug" used in Paragraph 5 means ______.

A．the danger of viruses
B．the common existence of virus particles
C．the short life span of viruses
D．the difficulty in killing viruses

A．We don't need to worry too much about bacteria everywhere in our life.
B．Antibacterial products for the home are found to be effective.
C．The TV advertisement the writer mentioned is a total failure.
D, The existent bacteria pose a threat only to the very young and very ol