10. Which of the following cell activation sequences most accurately represents sensitization in type 1 hypersensitivity reaction? (A) B cells stimulate cytotoxic T cells to activate T helper 1 cells. (B) T helper 1 cells stimulate T helper 2 cells to activate class switching of B cells. (C) Dendritic cells stimulate T helper 2 cells to activate class switching of B cells. (D) Dendritic cells stimulate T helper 1 cells which activate cytotoxic T cells. (E) cytotoxic T cells stimulate T helper 2 cells to activate class switching of B cells.