人体中哪些组织属于中等声衰减()
A．肝脏
B．肌肉
C．脑
D．肾脏
E．以上都是
参考答案：E
―I called you this morning, but nobody answered.
―I ______ the flowers in my garden at that time.[ ]
A. watered
B. was watering
C. water
具有平面孔系的零件，孔的数量较多，宜采用点位直线控制的数控（）或数控镗床加工。
A、钻床
B、铣床
C、车床
D、加工中心
