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    Helen is an English schoolgirl. She is now in Nanjing with her parents. She doesn't know Chinese. She often tries to speak Chinese to her Chinese friends. Sometimes they don't understand(理解) her, because she can't speak Chinese well.
    It's a Sunday morning. Helen wants to go to Zhongshan park. She is going there to see a flower show(展览). But she doesn't know how to go there. She asks a Chinese boy. The boy can't understand her. Then she takes out a pen and some paper. She draws a park and some flowers on it and gives the picture to the boy and says something about it. The boy smiles and then shows Helen the way to the park.

在正四棱锥S-ABCD中，侧面与底面所成的角为，则它的外接球半径R与内切球半径之比为（　）

用84cm长的铁丝围成一个三角形，这个三角形三条边长度的比是3∶4∶5．这个三角形的第一条边是____厘米？第二条边是____厘米？第三条边是____厘米？

The picture is ______ at least twenty pounds.

下列句中划线成语使用恰当的一项是（   ）