[名词解释] 颔厌

何谓发动机的发火间隔角？四缸和六缸四行程发动机发火间隔角各为多少？ 可直接用氢氧化钠滴定液滴定的药物有（） ["A、氨甲苯酸","B、水杨酸钠","C、布洛芬","D、甲芬那酸","E、乙酰水杨酸"] 面颈部皮下脂肪分为几个区（）. ["A、1","B、2","C、3","D、4","E、5"] 上关 SMAS向下移形为（）. ["A、颈阔肌","B、斜方肌","C、胸小肌","D、胸大肌","E、胸锁乳头肌"] 颔厌