两个相邻自然数的和是97,这两个自然数是____ 和____ .
I saw him in the library yesterday. He a book at that moment.
鲫鱼的口和鳃盖后缘不停地相互交替张开和紧闭,其作用是( )
切西瓜时会流出许多汁水,这些汁水是西瓜细胞的( )