Look! Is a girl ____ on the grass?[ ]
A. dances
B. dancing
C. dance
D. to dance
答案:B
A.mgtgθ
B.mgsinθ
C.μmg
D.μmg
早、中期食管癌常用的手术方法是
A.食管胃转流术B.食管癌切除,用结肠食管重建术C.食管癌切除,用胃食管重建术D.食管癌切除,用空肠食管重建术E.胃造瘘术