骨骼肌收缩活动的基本单位是（）
A、肌纤维
B、肌原纤维
C、肌丝
D、肌小节
参考答案：D
China is becoming stronger and stronger. It is no longer_________ . [ ]
A. what it used to be
B. what it was used to being
C. what it used to being
D. what it was used to be
权力机关、人民政府以及上级公安机关，可以通过检查、审查、调查等监督形式对公安执法行为进行监督。 ( )
