Your eye is a window on the nerves and blood vessels, revealing vital information about your entire body. An (1) exam starts from the outside and works in. First the ophthalmologist (眼科医生) gauges (2) with the familiar wall chart and checks visual field by moving objects in and out of (3) . A limited visual field could be the (4) of the high inner eye pressure of glaucoma(青光眼)or (5) a tumor pressing on nerves leading from the eye. The physician also checks for infection around the lashes and notes how fast the lids follow the eyes downward. Lid lag sometimes (6) thyroid disease (甲状腺疾病).If one pupil contracts (7) the other doesn’t, the physician is (8) to the fact that (9) a tumor or stroke, perhaps, has damaged the nerves between the eye and brain. A tumor as far away (10) the lung can cause capillary problems by hitting a nerve that loops through the neck.The white of the eye, tear ducts, lens and retina (视网膜) are checked for (11) of trouble. Too many white blood cells (12) inflammation, blood means tissue has tom or a vessel has burst, and deposits of (13) material can mean eye disease. The orange-red retina holds many more (14) for disease detection. High blood pressure may announce its (15) by pushing the vessels off track at their intersections. (16) vessel growth is a sign of diabetic retinopathy (糖尿病性视网膜病). Narrowed vessels may indicate (17) of the arteries, and damage to tiny capillaries could be a sign of early diabetes.The doctor even examines the pin-head-size hole in the back of the optic nerve on their way to the brain. (18) the appearance of these nerve fibers is abnormal, nerve tissue may have been damaged because of intraocular pressure, indicating glaucoma or the presence of a tumor. When a physician needs quick, (19) information about the body, the eyes have (20) . Read the following text. Choose the best word(s) for each numbered blank and mark A, B, C or D on ANSWER SHEET 1.7（）

A. but
B. when
C. or
D. as