题目内容：
Lowering the Risk of Heart DiseaseLike millions of other Americans, I come from a family with a history of heart disease. My father had his first three heart attacks when he was only thirty-0ne. ______(46)I grew up with heart disease: It was there, but I didn't take it seriously.
When I was thirty-one, my blood cholesterol (胆固醇) level was measured for the first time. It was 311 mg/dl, the doctor told me — an extremely high level that put me at a very high risk of heart disease, especially with my family history. He sent me to the National Institutes of Health (NIH) to be screened for participation in a clinical trial.______ (47)
At NIH, physicians explained the degree of risk associated with my blood cholesterol level and the nature of the experiment. This test involves putting a tube through a leg artery (动脉) up to the heart.______(48)
Learning about the risks of the experiment as well as the risk associated with my raised blood cholesterol level scared the life out of me. Although I was excluded from participating in the study, the experience may well have saved my life.
For the first time, I began to realize the seriousness of high blood cholesterol.______ (49)But equally important, I got a taste of what it is like to be a patient, to have tests done on me and to think of myself as sick. This was hard to take.
This experience taught me two lifesaving lessons. First, although I felt fit and strong , I was actually at high risk for heart disease because of my high blood cholesterol level. And with my family history, it could not be ignored. ______(50)
A The death rate for the test was only 1 in 100, I was assured.
B Second, I could lower my blood cholesterol level simply by changing what I ate.
C I was three years old at that time.
D There is not enough oxygen in the blood.
E It was a heart attack just waiting to happen.
F The trial was designed to test the effect of lowering blood cholesterol on the risk of heart disease.
请选择（46）处的最佳答案．
参考答案：
答案解析：