Nina has the flu and a high fever. her immune system is exhibiting the; 2nd 1st or 3rd line of defense. this defense is part of adaptive, innate or acquired immunity.

Nina is showing the second line of defense. This line is part of the acquired immunity.

Explanation:

The acquired immunity is part of the organism's second line of defense and is established with the organism's contact with foreign molecules that can cause harm such as viruses, bacteria, among others. The acquired immunity has the function of removing the invader that is already exposed to the cells of the organism, guaranteeing an immediate response to its attack.

When a virus, type a that causes the flu, attacks the organism's cell, the acquired immunity recognizes that virus and works to neutralize the infection and expel the foreign organism. As a result, the infected individual may experience symptoms such as coughing, sneezing and fever, until his acquired immunity is able to expel the virus.