Answer:
Mouth is the first portion of the alimentary canal that receives food and produces saliva.
As you have probably guessed, the main function of the muscular system is movement, but it also helps stabilize our joints, maintain our posture and generate heat during activity. Movement of our body can be voluntary and controlled by the skeletal muscles, or it can be involuntary and controlled by smooth muscles.
The passing of genetic material from parents to offspring is called Heredity.
Thus, C, is your answer.
Amount of wear, and how long they are may contribute with age and maybe even coloration and pigment.
