Answer the following question given this paragraph: 

Most plasma cells live for just a few days, but some of them live much longer. They may even survive for the lifetime of the individual. Long-living plasma cells are called memory cells. They retain a “memory” of a specific pathogen long after an infection is over. They help launch a rapid response against the pathogen if it invades the body again in the future.


Q: What are long living plasma cells called?

 Choices:

- device cells

- context cells

- brain Cells

- memory cells

A:
memory cells
