Read the following passage and mark the letter A, B, C, or D to indicate the answer to each of the question.

Most of us have a sweet tooth. We love to eat a cookie, a donut or a piece of chocolate. But have you noticed what often happens when you eat one? When we eat or drink sugary foods, the sugar enters our blood and affects part of our brain. We may feel better, but the good feeling stops and we just want another one. All tasty foods do this, but sugar has a particularly strong effect. This is why many scientists believe that our love of sugar might be an addiction. In the body, sugar acts like an addictive drug, one that doctors recommend we all cut down.

It seems obvious now that too much sugar can harm us, but why is it harmful? In early human history, the body began storing sugar as fat to use as energy. Our bodies are efficient, so they need very little sugar. Today, the Western diet has the highest amount of sugar in history. There are also more high blood pressure and diabetes in the world. Some researchers believe that too much sugar may be the culprit.

How do we battle our sweet tooth? Doctors advise us to cut down on sweets. They recommend that we choose healthy foods for snacks. Nuts, dark chocolate and yogurts are some of them. Yet even healthy foods can have too much sugar. Yogurts that are advertised as low-fat can have 17 grams, about half the daily allowance. However, the less sugar you eat, the less you want. Exercise helps, too. Using facilities such as walking tracks and gymnasiums can help control our desire.

(Adapted from Reading Explorer 2, Paul MacIntyre et al., 2015)

The word "that” in paragraph 3 refers to _______.