下列各项中，属于按照产品数量分类的是( )。
A．抽样检验
B．流动检验
C．固定检验
D．最终检验
参考答案：A
The experiment shows that proper amounts of exercise. if ____ regularly. can improve our health. [ ]
A. being carried out
B. carried out
C. carrying out
D. to carry out
叠音又称（），指相同字（）的重叠。叠音是汉语语音修辞的重要手段。
if ____ regularly. can improve our health. [ ]