I believe it would be sperm
Dideoxynucleotides are chain-elongating inhibitors of DNA polymerase, used in the Sanger method for DNA sequencing.
The pair of structures that share the function of reabsorbing water into the body us the Hypothalamus and Pancreas.
The efficiency indicates the manner in which the inputs are used by the system. Being efficient means the system uses inputs in a `right' way. If the input-output ratio is adverse, we say that the system is inefficient though it produces the desired output.