A person who has AIDS contracts rare and often life-threatening infections because their helper T cell count is so low. Which of the following components of the immune response still respond to antigen despite the low helper T cell count?
Clonal selection of B cellsActivation of cytotoxic T cells by helper T cellsagglutination

CLONAL SELECTION OF B CELLS.

Explanation: B cells are also known as B lymphocytes( a type of white blood cell),when antigens binds to receptors in the cell,B lymphocytes in the body recognizes this antigen and selection is made from the pre-existing pool of different antigens,each with it's unique specification,this B lymphocytes undergo reproduction and from there a clonal population of cells are formed which kills/get rid of the antigen.

These antigens are eliminated by either the plasma cells that form immediately from the B lymphocytes secreting antibodies that fight the antigen,but in AIDS (people living with AIDS),the B lymphocytes that fight the antigen are known as memory B cells which are long lived from the stage of proliferation and are left to fight antigens in later life by forming plasma cells.so even if the helper T cells in AIDS patients are low,the memory B cells are stimulated to form plasma cells,activate antibodies to fight off life threatening infections.

you must remain stopped until the stop signal is retracted and the red lights are turned off. approaching traffic in the opposite roadway of a divided highway shall not be required to stop, even if the school bus has the stop-arm extended and the alternately flashing warning signal lamps on.

the answer is c a tornado