I ____ (talk) with some friends last night.
How is the weather?____
开关S闭合后,小磁针静止时的指向如图9-3-8所示。由此可知( )图9-3-8
用如图所示的装置探究凸透镜成像规律.凸透镜的焦距是15cm.当把凸透镜固定在50cm刻度线处,蜡烛固定在15cm刻度线处时( )
小小书法家。比一比谁写得最漂亮。
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