The World Health Organisation defines adolescents as individuals in the age-group of ______.

10 to 19 years

The correct answer is Option (1) → 10 to 19 years

The World Health Organisation (WHO) defines adolescents as individuals in the age group of 10 to 19 years old. This is a crucial stage of development marked by rapid physical, cognitive and psychosocial changes. It's an important time for laying the foundations of good health throughout life.