[问答题]
The graph shows the typical i5p yo*w + b7p.rvyzn5hmmune jk.) iqo73ss 9 p-j4qych5wp6my i.m jresponse to two doses of a vaccine.
1.State which type of molecule stimulates antibody production.
2.Distinguish between the primary and secondary responses.
3.Explain how vaccination leads to long-term immunity.
