Four groups of students (A-D) were asked to determine whether memory B cells generated in mice immunized with ovalbumin (OVA), in Complete Freund's adjuvant (CFA), could mount a secondary antibody response (recall response) to OVA in vitro. The groups did the following experiments:

Group A students harvested serum from the mice, loaded it on OVA-coated ELISA plates and showed that lgG and lgA anti-OVA antibodies were present.

Group B students harvested long-lived plasma cells from bone marrow of the mice, plated them in culture for 5 days and showed anti-OVA antibodies in supernatant by ELISA.

Group C students infected an epithelial cell line with the virus and showed that spleen cells from the mice could kill the infected targets.

Group D students stimulated spleen cells from the mouse with OVA for 5 days and showed anti-OVA antibodies in supernatant by ELISA.

Which one of the following options represents group(s) that did the correct experiment?