Which of the following statements about sunspots is false?
a. they are areas of the sun that are "burnt out."
c. they are cooler than the surrounding areas of the sun.
b. they occur on the surface of the sun.
d. they occur in cycles.

A. These areas of the sun are not "burnt out." They are areas on the sun's surface (C) that are cooler than the surrounding areas (B) caused by cyclical fluctuation of the magnetic field due to convection and radiation taking place on the sun (D).

The answer is ozone layer.

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.