Which of the Following Statements About Memory Cells Is True

Which of the following statements about memory cells is true?

A) They include B cells and T cells that remain in the body for long periods of time after the first exposure to a pathogen.
B) They are macrophages that store copies of antibodies for decades.
C) They make copies of T cells that remain active long after the primary response has ended.
D) They become T cells during a secondary response to a pathogen.