Which of the following statements best describes a role of beneficial bacteria in
an ecosystem?
O
They make nitrogen available to other organisms.
O
They use many of the nutrients in the atmosphere
O
They release chemicals that are toxic to certain living things.
O
They exchange gases with their surrounding atmosphere.

The answer is letter b

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.

The answer is d. when it begins to fall back to the child's hand