Answer:
A. human genetic similarities.
Step-by-step explanation:
Every basic physical features that humans can do without external learning are influenced by our genetic. Genetic similarities resulted in almost identical physical components that exist between humans regardless of our races.
When we examine people with different races, we will find that our physical mechanism are extremely similar with one another. Our bodily function are similar , the range of emotions that we feel are the same, Our tendency to make facial expressions in response to our emotions are also the same , etc.