已知△ABC∽△DEF，△ABC与△DEF的相似比为4：1，则△ABC与△DEF对应边上的高之比为____．

探究：有一弦长6cm，宽4cm的矩形纸板，现要求以其一组对边中点所在直线为轴，旋转180°，得到一个圆柱，现可按照两种方案进行操作：

方案一：以较长的一组对边中点所在直线为轴旋转，如图①；

方案二：以较短的一组对边中点所在直线为轴旋转，如图②．

（1）请通过计算说明哪种方法构造的圆柱体积大；

（2）如果该矩形的长宽分别是5cm和3cm呢？请通过计算说明哪种方法构造的圆柱体积大；

（3）通过以上探究，你发现对于同一个矩形（不包括正方形），以其一组对边中点所在直线为轴旋转得到一个圆柱，怎样操作所得到的圆柱体积大（不必说明原因）？

    I was on my way home with a friend yesterday ____ I found a mobile phone by the roadside. After picking it up, I suggested that we go to the house in front of which we found the mobile phone. And we did so. I ____ (knock) at the door and two young men answered. Neither of them had lost ____(they) phones, but as I referred to some names on the contact list(通讯录), one of them said he also had those ____(name) and that it must be the phone of one____their friends. Then, he took the phone and said how wonderful it was that I took the time____(find) the owner. Afterwards, I left without ____(leave) my name or address. I never considered keeping the phone. Instead, I immediately tried to find ____ owner. And I believed that was ____(exact) what I would want someone to do if I lost my phone. It couldn't have been ____ (good).

    Sometimes, helping others is just doing the right thing.

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