From the list of available choices, the most likely reason why genetically modified humans do not occur is Ethical concerns
This refers to the term that is used to refer to the use of genetic engineering to create humans with specific features and abilities.
Hence, it can be seen that the forefront reason why genetic engineering on humans are not so widespread is as a result of ethical concerns which comes from "playing God"
Read more about genetic modified humans here:
https://brainly.com/question/2780091
#SPJ1