78. 下列哪兩組肌肉共同作用的效果在力學上稱為力偶（force couple )? (A)棘上肌(supraspinatus)與棘下肌(infraspinatus) (B)菱形肌(rhomboids)與肩胛下肌(subscapularis) (C)下斜方肌(lower trapezius)與前鋸肌 ( serratus anterior) (D)提肩胛肌(levator scapulae)與胸小肌 (pectoralis minor)