What are two parts to a controlled experiment

You can control time in a experiment EX: say you let a plant sit in the sun for 5 hours and then let another plant sit for an entire full 24 hours and see what's the effect well what you controlled there was the time and your dependent variable would be what ever happened to that plant.  so you can control time and you can control speed if its an object that acquires you to exert force. 

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.