The graph illustrates how the concentration of antibodies in a child’s blood changes over time. It indicates the changes in antibody concentration after the child has been vaccinated against a specific disease and after the child has been infected by the pathogen responsible for that disease. From the graph, which statement is correct?
- AMemory cells have disappeared from the child’s blood by 3.
- BMemory cells were in the child’s blood at 2.
- CMemory cells were in the child’s blood before 1.
- DPassive immunity was attained at 4.