The diagram illustrates how the immune system responds to a pathogen. Which row correctly identifies P, Q, R and S?
- AP: antibody, Q: T-lymphocyte, R: antigen, S: plasma cell
- BP: antigen, Q: B-lymphocyte, R: antibody, S: memory cell
- CP: antigen, Q: T-lymphocyte, R: antitoxin, S: B-lymphocyte
- DP: bacteria, Q: B-lymphocyte, R: antibody, S: T-lymphocyte