阅读下面短文，从每小题所给的A、B、C、D四个选项中选出最佳选项。
How many calories (卡路里) are there in every meal you eat? That seems like a difficult question to answer. But students at Aitkin High School in the United States can easily answer it now. They put what they eat into an online calorie counter (计算器). It quickly tells how many calories there are in their meals.
In fact, this is part of the school's health class. It is about heart health, nutrition (营养), and fitness. Students can learn basic knowledge about fats, proteins (蛋白质), calories and sugar. Students can also learn how to balance calories in and out. They will know what happens when the balance isn't there. "The online calorie counter can help you make healthy choices. Making one healthy eating decision can really make a difference," Adam Carlson, the teacher of the class, told local newspaper Aitkin Independent Age.
They also talk about good ways to burn calories in the gym. According to Carlson, the gym is a great place to burn calories and get stronger. But it doesn't work for everyone. So they try to find different ways to exercise. "I'm trying hard to teach the students that doing exercise can be fun but hard, and doesn't need to take hours out of the day, but you should keep on doing it for a long time," she said.
The class has changed students. "I am now watching what I am eating and pay attention to the food labels (标签)," said seventh-grader Karena Burgstaler. Another student James Erickson began to pay attention to how much sugar he eats because it was almost over his daily calorie intake goal.
