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.