Which of the following functions belongs to the cellular membrane?
a. keeps the organelles in place.
b. protects the cells from its surroundings.
c. acts as an "id card" for cells
d. allows large molecules to move from one side of a cell.

The answer is joseph is observing the colour of the reaction mixture to see whether proteins are present in the given solution.

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.