单选题
Over 2 million Canadians have diabetes. It is the leading cause of blindness in North Americans under 65 years of age. Diabetes is a condition where the body either cannot produce enough insulin (胰岛素) or cannot respond properly to insulin. Insulin is important because it moves glucose (葡萄糖), a simple sugar, to the body"s cells from the blood. The food people eat provides the body with glucose, which is used by the cells as a source of energy. If insulin isn"t available or doesn"t work correctly to move glucose from the blood into the cells, glucose will stay in the blood, leading to high blood sugar levels.
High blood sugar levels damage the blood vessels, including the tiny blood vessels in the eye. This leads to an eye disease known as diabetic retinopathy (糖尿病型视网膜病). The retina (视网膜) is an area at the back of the eye that changes light into nerve signals. With diabetic retinopathy, some blood vessels in the retina are lost, and some of the other blood vessels begin to "leak" blood. This causes the retina to swell, and gradually cuts off its supply of oxygen and nutrients (滋养物 ). Eventually, the retina starts to grow new blood vessels to replace the damaged ones. Unfortunately, these new vessels are not as strong as the old ones. They are more likely to break, causing bleeding in the eye.
At first, people with diabetic retinopathy will not notice any symptoms. As the disease gets worse, they may notice blurred (模糊地) vision, black spots or flashing lights. As time goes on, it can progress to blindness. Everyone with diabetes is at risk for diabetic retinopathy, and the risk increases the longer you"ve had diabetes.
Fortunately, you can reduce your risk. If you do not have diabetes, but think you may be at risk for this condition, visit your doctor to be screened for diabetes. If you do have diabetes:
· Have frequent eye check-ups.
· Make sure that you monitor your blood sugar frequently and use your medications as recommended by your doctor. There is evidence to show that keeping your blood sugar under tight control can slow down eye damage.
·If you have high blood pressure, follow your recommended diet and medications to keep it under control. If you are not sure whether you have high blood pressure, or whether your blood pressure is under control, discuss this with your doctor.

单选题 Glucose cannot be turned into energy in the body ______.

单选题 The word "its" in the second paragraph refers to ______.

单选题 With diabetic retinopathy, the damaged blood vessels in the retina ______.

单选题 The worst eye damage induced by diabetes is ______.

单选题 To slow down eye damage, people with diabetes should try to ______.