What did Frank and his father do yesterday?
A:They went to the library.
B:They went swimming.
C:They played chess.
根尖结构中,吸收水分和无机盐的主要部位是 ( )
“穿花蛱蝶深深见”、“青草池塘处处蛙”,这两句诗中描述的蛱蝶和蛙在生殖和发育方面的相似之处是( )
如图,晚上小明由甲处径直走到乙处的过程中,他在路灯M下的影长在地面上的变化情况是( )