Indicate whether each of the following descriptions better applies to B cells (B) or T cells (T) of the adaptive immune system. Your answer would be a four-letter string composed of letters B and T only, e.g. BTTT.
( ) Their effector cells act mainly at short range.
( ) Their receptors recognize protein fragments that have been processed in antigen-presenting cells.
( ) They do NOT normally express CD8 protein on their surface.
( ) They can become "killer" cells.