30. 出現跛行現象(Trandelenberg sign)時為哪一肌肉無力所致？ (A) 承重側(single support side)的臀大肌(gluteus maximus) (B) 非承重側(non-weight bearing side)的臀中肌(gluteus medius) (C) 非承重側(non-weight bearing side)的臀大肌(gluteus maximus) (D) 承重側(single support side)的臀中肌(gluteus medius)