Correct answer : B). People do not have immunity to a new strain of the influenza virus.
The main problem with the influenza virus is that these viruses constantly changes their DNA, this allow them to invade the immune system. It works as follows, if a person is affected by the influenza virus then the body prepares antibodies against it.
But influenza virus changes its genetic makeup after sometime, so the older antibodies will not be able to recognize the new virus and the body get infected. That is the main reason for the outbreak of the influenza virus
Hence, the correct answer would be option B.
