奶牛，4岁，轻度跛行，左前肢蹄球部相邻的皮肤充血肿胀，增厚，指间隙有渗出物，呈腐败臭味，压诊患部有痛感。该牛最可能患的蹄病是（）

A.腐蹄病

B.蹄叶炎

C.局限性蹄皮炎

D.指（趾）间皮炎

E.指（趾）间皮肤增生

_________ you take an active part in physical activity ______ be able to keep fit and stay healthy.

A．Only if; you will

B．Only if; will you

C．Unless; you will

D．Unless; will you