Mitochondria are organelles in which 1. digestive enzymes are stored 2. secretory products are packaged and stored 3. the energy needed by the cell is released from nutrients 4. chloroplasts and nutrients

A mitochondria is the powerhouse of the cell so i'm assuming CHLOROPLASTS AND NUTRIENTS 

I believe that it's 3. The energy needed by the cell is released from nutrients.

answer: - b cells

explanation: -

there are many types of white blood cells present in our body. one such class of white blood cells are the lymphocytes. the b cells belong to the lymphocyte class of wbcs. the b cells perform their action against the pathogen by producing specialised proteins called as antibodies. these antibodies are produced as and when the b cells encounter pathogens in response to the antigens present on the surface of the pathogen. these antibodies bind to the antigens present on the pathogen and then, target them for destruction by other cells of the immune system.

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.