【单选题】
Blood pressure is simply the force {{U}} (53) {{/U}} against the walls of the body’s arteries (血管) as blood flows through. The force, produced primarily by the pumping {{U}} (54) {{/U}} of the heart, is essential for the {{U}} (55) {{/U}} of the blood and its life-supporting nutrients(营养) to all parts of the body.Every time the heart {{U}} (56) {{/U}}, called a systole, blood pressure increases. When the heart relaxes {{U}} (57) {{/U}} beats(diastole), the pressure decreases. The normal systolic pressure of a person at vest is between 100 to 140, and the normal diastole is 60 to 90.Blood-pressure readings are expressed by both {{U}} (58) {{/U}}, with the systolic over the diastolic: for example, 140/90.
As these ranges suggest, there is a wide {{U}} (59) {{/U}} of blood pressure for healthy people.Also, blood pressure {{U}} (60) {{/U}} for healthy people during different times of the day and under different. {{U}} (61) {{/U}}. It is lower when an individual is asleep than when he is excited or exerting himself physically. Therefore, a single blood-pressure reading above 140/90 does not {{U}} (62) {{/U}} abnormality. When the pressure is continuously {{U}} (63) {{/U}}, a person is considered to be suffering from hypertension.
Hypertension is a stealthy(隐秘的) problem: a physician can discover it easily enough, but not a patient. {{U}} (64) {{/U}} elevations, for example, may produce headaches, dizziness, fatigue, and weakness.But the patient is not likely to {{U}} (65) {{/U}}these symptoms as having any other source than the increased elevation.
B．compresses
C．concentrates
D．contracts
网考网参考答案：D
网考网解析：
[词义辨析] contract意为“收缩”；compress意为“压缩”；condense意为“使……冷凝、缩合”。D合句意。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>
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