Which of the following is true of adaptive immunity?

A) It is present at birth.
B) Previous encounters with the foreign substance does not change the response.
C) The second response is faster and stronger than the first response.
D) Responses are general, not specific.

Adaptive immunity is characterized by its ability to remember previous encounters with pathogens, leading to a faster and stronger response upon subsequent exposures. This is in contrast to innate immunity, which is present at birth and responds in a general, non-specific manner to pathogens.