创建全国文明城市要求注册志愿者人数应该占城市人口总数的多大比例？

行走运动中控制伸髋屈膝的主要肌肉是（）

A.股四头肌

B.腘绳肌

C.骶棘肌

D.臀大肌

E.胫前肌

In my opinion,all Mr White________good to his students in his class at present.He is very strict

in their study.[      ]

A. does does does    

B. does do do

C. does does do  

D. did do does

上颌第二前磨牙单根者比率约为( )

A．20%

B．40%

C．60%

D．80%

E．90%

提高农业劳动生产率的途径有哪些？

请写出投料前更换工艺烧嘴的步骤。