<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A researcher is studying the interactions between foreign antigens and human immune cells. She has isolated a line of lymphocytes that is known to bind antigen-presenting cells. From this cell line, she has isolated a cell surface protein that binds the constant portion of the class I major histocompatibility complex molecule. The activation of this specific cell line requires co-activation via which of the following signaling molecules?? A: Interleukin 1, B: Interleukin 2, C: Interleukin 4, D: Interleukin 6, E: Interleukin 8,  <response>: This question is asking about the signaling molecule required to activate a specific lymphocyte cell line that binds to antigen-presenting cells. The key details are:- The lymphocytes bind antigen-presenting cells - They have a cell surface protein that binds MHC class I molecules- Co-activation of a signaling molecule is required for activationThis suggests the lymphocytes are T cells, since they bind MHC molecules. T cell activation requires signaling from the T cell receptor as well as co-stimulatory signals like cytokines. Of the choices, interleukin 2 IL-2 is the main cytokine that provides co-stimulation to activate T cells. The other interleukins have different roles.B: Interleukin 2 