关于螺旋器的描述，正确的是（）.A.感受头部的旋转运动 B.毛细胞上有许多动纤毛 C

For how many integers n is 2ⁿ=n² ？（）

A.None

B.One

C.Two

D.Three

E.More than three

Since he started high school, he’s come to school by bike_____.     [ ]

A. on his own  

B. by his own    

C. in his own    

D. with his own

锤式破碎机为什么不宜破焦粉？

破乳剂一种具有良好的（）和足够的絮凝、聚结能力，使乳化体系很快破乳的表面活性剂。

A.氧化性

B.润湿性

C.还原性

D.耐腐蚀性