He is busy practicing _______English. [ ]
A. speaking
B. to speak
C. speak
答案:A
分解因式:a3﹣8a=( )
下列哪组食物有利于维持皮肤光滑( )
A.猪肝、胡萝卜
B.蔬菜、水果
C.鱼、肉
D.牛奶、豆制品