First of all, it is important to understand the difference between passive and active immunity.
Passive immunity is when we are given antibodies that were not produced by our own body (for example those transferred from mother to child, or those taken as part of medication or therapy - note that the former would be an example of naturally acquired passive immunity and the latter of artificially acquired passive immunity).
Active immunity, on the other hand, refers to antibodies that were produced by our own bodies due to exposure to a pathogen or part thereof - this can also be naturally acquired, such as when we are infected by a pathogen, or artificially, such as when we are vaccinated.
Given this information, what enabled Gina to fight the pathogen would be the second answer (antibodies she received from her mother), however we can also look at the other answers and discount them as false to be sure:
Answer 1 - high fever caused by a pathogen
The question states that Gina was able to fight off the pathogen before she got sick - a fever suggests that:
a) she is already sick
b) her body is launching its own immune response
Answer 3 - antibodies she received from a vaccination
The antibodies produced as a result of vaccination are produced by your own body (despite being stimulated artificially through exposure to the pathogen), thus this is not the correct answer.
Answer 4: inflammation caused by antibodies
This answer is incorrect due to the fact that antibodies do not directly cause inflammation.
Thus, the correct answer is the second one 'antibodies she received from her mother'.
Hope that helps :)
