Option is the correct answer as acquired immunity is a specific type of defence which is not present at the time of birth.

Option , and are true statements and hence cannot be the answer.

Anamnestic response or secondary immune response is a highly intensified response due to memory of first encounter. When our body encounters a pathogen for the first time then the body elicits the primary immune response, When there is a subsequent encounter with the same pathogen, secondary or anamnestic immune response is elicited.

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