If you toss a coin five times and it lands heads up each time, can you expect the coin to land heads up on the sixth toss? explain.

There is still a 1/2 chance that the coin can land heads up. You shouldn't expect it to land on heads. because the chance is equal to landing on tails. Either can happen with an equal chance. 

Spherical shaped cell might increase the surface area and decrease the volume.

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.