Immunological memory accounts for what? a) the ancient observation that someone who had recovered from the plague could safely care for those newly diseasedb) the human body's ability to distinguish self from nonselfc) the ability of the immune system to present antigen fragments in association with mhc antigensd) the observation that some strains of the pathogen that causes dengue fever cause worse disease than otherse) the ability of a t-cells to signal b-cells via cytokines

C) The ability of the immune system to present antigen fragments in association with MHC antigens

Explanation:

During the process of building the immune response against some antigen, an enormous amount of cells are responsible for this antigen recognition and attack.

These extremely antigen-specific cells play an essential role in the presence of the antigen, but at the end of the response, when the antigen has been completely eliminated, this amount of specific cells, being unnecessary, must be eliminated in order to cause no damage to the antigen, as well as saving unnecessary energy costs.

At this moment, most of these cells, no longer needed, die. However, not all of these specific cells die, and these remaining cells are called memory cells.

Thanks to memory cells, every time the individual comes back into contact with the same antigen, these cells will recognize it and divide rapidly, so the immune response is faster and more intense than the first time, this process is called immunological memory.

To maintain immunological memory function, the immune system acts in conjunction with the Major Histocompatibility Complex (MHC). This complex recognizes and prevents a foreign body from entering and spreading through the body, triggering immediate response against these foreign bodies.