a.stabilizing selectionStabilizing selection is when the environment the organisms live on favors the middle type of species among the various type of allele. Such as the normal sized mice is favored from the rest. Thank you for your question. Please don't hesitate to ask in Brainly your queries.
No because if the body never met the pathogen before so the immune system would not have had any reason to make an antibody against it because body makes antibodies against specific pathogen :)) i hope this be helpful