The branch of biology dealing with the process how to improve the human race by selective breeding is:

A. Euthenics

B. Obstetrics

C. Euphenics

D. Eugenics

Eugenics is the branch of science which deals with improvement of human race genetically. This aspect of human betterment aims to improve the human germplasm by encouraging the inheritance of best characteristics so that defective characters may be eliminated.
 
hence option D is correct