Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42.

Childhood obesity is a serious medical condition that affects children and adolescents. It's particularly troubling because the extra pounds often start children on the path to health problems that were once considered adult problems. Treating and preventing childhood obesity helps protect your child's health now and in the future.

Some children have larger than average body frames. And children normally carry different amounts of body fat at the various stages of development. So you might not know by how your child looks if weight is a health concern. The body mass index (BMI), which provides a guideline of weight in relation to height, is the accepted measure of overweight and obesity. [1] Your child's doctor can use growth charts, the BMI and, if necessary, other tests to help you figure out if your child's weight could pose health problems. [2]

Lifestyle issues — too little activity and too many calories from food and drinks — are the main contributors to childhood obesity. But genetic and hormonal factors might play a role as well. Childhood obesity often causes complications in a child's physical, social and emotional well-being. Physical complications of childhood obesity may include type 2 diabetes, joint pain, breathing problems, high cholesterol and high blood pressure. Children who have obesity may experience teasing or bullying by their peers. This can result in a loss of self-esteem and an increased risk of depression and anxiety.

To help prevent excess weight gain in your child, there are many things you can do such as making healthy eating and regular physical activity a family affair. Everyone will benefit and no one will feel singled out. You can choose snacks like air-popped popcorn without butter, fruits with low-fat yogurt, baby carrots with hummus, or whole-grain cereal with low-fat milk. And you should know that promising candy for good behavior is a bad idea. Some studies indicate that too little sleep may increase the risk of obesity. Sleep deprivation can cause hormonal imbalances that lead to increased appetite. Also, be sure your child sees the doctor for well-child checkups at least once a year. [3] A significant increase in your child's BMI percentile rank over one year may be a possible sign that your child is at risk of becoming overweight. [4]

(Source: https://www.mayoclinic.org/)

The word “This” in paragraph 3 refers to _____.