Studies show muscles which are not 56 lose their strength very quickly.To regain it needs 48 to 72
问题描述：
Studies show muscles which are not 56 lose their strength very quickly.To regain it needs 48 to 72
Studies show muscles which are not 56 lose their strength very quickly.To regain it needs 48 to 72 hours and exercise every other day will 57 a normal level of physical strength.
56.A.exercised B.examined C.protected D.cured
57.A.lose B.raise C.burn D.keep
答
56.A
Excercise muscles:锻炼肌肉.句意是“研究表明未经锻炼的肌肉会很快失去力量”
57.D
Keep a normal level：保持正常水平.因为句中说的是“excercise every other day”,即有规律的锻炼,所以可以维持正常的体能水平.