The nurse is providing care for a client who underwent mitral valve replacement. The best example of a measurable client outcome goal is to

A. change his own dressing.
B. walk in the hallway.
C. walk from his room to the end of the hall and back before discharge.
D. eat a special diet.

骨质疏松症是一种能够减轻骨骼质量从而导致骨骼易折断的疾病，现在的疗法如雌性激素和降钙素疗法只能阻止骨骼质量进一步的减少而不能重新补回所失质量。由于氟化物可增加骨骼质量，因此给患有奥氏病的病人服用氟化物将会使其骨骼不那么易折断。
以下哪项如果为真，最能削弱上述论证的可信度( )

A．大多数患奥氏病的人并未意识到服用氟化物能够增加骨骼质量

B．许多地方人们将氟化物溶于饮用水中以使饮水者的牙齿更加坚固

C．患奥氏病及其他骨骼退化类疾病的几率可通过锻炼与适当摄入钙质而降低

D．服用氟化物后生成的骨质要比正常骨质脆且弹性小