Repair systems that target a single type of damage in dna and repair only that type of damage are called systems.

I believe the answer is Specific repair systems. These types of repairs target a single kind of lesion or damage and repair only that damage.DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecule that encodes its genome. DNA damage may result from both metabolic activities and environmental factors such as radiation. 

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.