شرکت در آزمون آنلاین زبان انگلیسی 1 - زبان انگلیسی 1 | آزمون شماره 12757

Carbohydrates, which are sugars, are a necessary part of a healthy diet. They give the main source of energy to the body, and they also function to flavor and sweeten foods. Carbohydrates range from simple sugars like glucose to complex sugars such as amylase and amylopectin. Nutritionists estimate that carbohydrates should make up about one-fourth to one-fifth of a person’s diet. This means about 75-100 grams of carbohydrates per day. A diet which doesn’t have enough carbohydrates can have a bad effect on the person’s health. When the body doesn’t have a sufficient amount of carbohydrates, it must then use its protein supplies for energy, a process called gluconeogenesis. This, however, can cause further health difficulties. The  absence of carbohydrates can also result in a number of health problems.

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The word “their” in paragraph 1 refers to … .