Final answer:
The behaviour of hair is affected by heredity, product use or appliances, and environmental factors, including lifestyle choices such as diet, exercise, and sun exposure.
Step-by-step explanation:
The three factors that affect the behaviour of hair are heredity, product or appliances, and environment. Environmental influences include both global aspects, such as climate and pollution, as well as personal lifestyle choices like sun exposure. Factors like poor hygiene can impact scalp health, leading to issues with hair. Some individuals may experience greying of hair as they age due to reduced melanin production. Lifestyle interventions, including modifying diet and exercise habits, may slow the rate of such age-related changes.