Answer:
b). activation of T cells
Explanation:
An APC (antigen-presenting cell) can be described as an immune cell, which detects, uptakes, and informs the acquired immune response when an infection takes place. B cells, macrophages, and dendritic cells are antigen-presenting cells.
These cells play an important role in activation of T cells. T cells are unable to recognize soluble or free antigens and can only recognize antigens processed and presented by carrier molecules, such as MHC molecules.
Presence of MHCII molecules is a defining feature of APCs that process and present antigens to T cells. Hence, all antigen-presenting cells help in activation of T cells.
Thus, the correct answer is option (b).