Also found in Paragraph 1, what does "this case study" probably refer to

A．A case study the writer is to talk about.

B．Part of a textbook on politics.

C．What the author is going to write.

D．Washington's inability to fool anyone.

如图为人体免疫部分过程示意图。请据图回答：

A、B的名称分别是（）、（）。