物理研究中常常用到“控制变量法”、“等效替代法”、“模型法”、“类比法”等方法,下面是初中物理中的几个研究实例: ①用总电阻表示同一段电路上串联的两个电阻;②用光线表示光的传播方向;③研究电流时把它与水流相比;④利用磁感线来描述磁场。上述几个实例中,采用了相同研究方法的是( )
A:①③
B:②③
C:②④
D:①④
Hello,I am Judy.In summer I like wearing a____.It is cool.In autumn I like wearing ____.I like hopping and jumping.In winter I like wearing a____.Because it is warm.What do you like,Jim? I like wearing sport____every day. Because I like running.How about you,Alice? I like____.This Sunday I will buy it.
世界上最长的山系是美洲板块与太平洋板块、南极洲板块相撞而形成的,它是( )