— What if our demand for more free time to learn by ourselves is not _________ by the school

       authority?  

— Hold on to it until we succeed. [ ]

A. approved      

B. arranged      

C. applied    

D. assisted

属于水平传播的是（）。

A.空气传播

B.经水传播

C.分娩时传播

D.经食物传播

E.经媒介节肢动物传播