A person’s intake of refined sugar and of foods that break down into sugars during digestion is the dietary source of virtually all of the glucose (a type of sugar) that reaches that person’s bloodstream. Coffee, however, which itself does not break down into sugars during digestion, sometimes causes a person’s blood-glucose level to rise dramatically, even if the coffee is consumed without cream or any sweeteners.
Which of the following, if true, best helps to explain coffee’s effect on blood-glucose levels as it is described above ？（）

A．People often drink coffee after a meal consisting of several types of foods that themselves rapidly break down into sugars during digestion.

B．Drinking more than two cups of coffee in an hour increases a person’s level of stress, and the body reacts to stress by releasing stored glucose into the blood.

C．People who eat very few foods that contain refined sugar often have higher blood-glucose levels than people who eat many such foods.

D．For many people, the consumption of one piece of chocolate cake has the same stimulating effect as one cup of plain coffee.

E．People with sedentary office jobs are more likely to drink large amounts of coffee and to have higher blood-glucose levels than are people with jobs requiring constant physical activity.

2006年，奇瑞汽车集团研发了一款新型汽车发动机，其冷却系统选择水作为工作物质是因为______，发动机的内能主要通过______而减小的．燃料燃烧产生的内能是通过______而转化为机械能的．目前，奇瑞轿车已奔驰在我国各地和世界部分国家，轿车里都要使用蓄电池，蓄电池使用前要先______，这个过程，把______能转化为______能．