耐蚀（酸）非金属材料，除具备良好的耐蚀性能外，还具有的性能为（）。A．耐急冷、急热性

下图人物受到百姓的爱戴，是因为他  

A．为治水三过家门而不入    

B．打败了蚩尤部落     

C．是部落联盟首领          

D．教人们挖井

速度和时间成反比例．______．

Tom sits ____ the classroom while John sits ____ the room. [ ]

A. in front of; at back of

B. in the front of; at the back of

C. in front of; at the back of

D. in the front of; at back of

能产生精子的器官是

A.肾 

B.睾丸 

C.前列腺 

D.卵巢 

E.精囊腺

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