According to the passage, what condition is responsible for many of the diseases of the old?

Đáp án A

Thông tin nằm ở đoạn 4: “One of the most serious changes of old age occurs in the arteries, the blood vessels that lead from the heart. They become thickened and constricted, allowing less blood to flow to the rest of body. This condition accounts, directly or indirectly, for many of the diseases of the aged. It may, for example, result in heart attack.”