Q16

The diagram shows the concentration of an antibody to a particular pathogen. Primary Secondary 2000 exposure to exposure to Concentration of antibody pathogen same pathogen (mg L–1) 1000 0 Time © Commonwealth of Australia (Geoscience Australia) 2019. This product is released under the CC Attribution 4.0 licence. Two students are exposed to the pathogen. Student X had previously been vaccinated against this pathogen. Student Y had never been exposed to it. Which row of the table shows the most likely levels of antibody in the blood of each student a week after exposure to the pathogen on this occasion?
Concentration of antibody in the blood ($\mathrm{mg\,L^{-1}}$)

	Student X	Student Y
A.	250	1500
B.	1500	1000
C.	1000	1500
D.	1500	250