一个圆柱的底面半径扩大到原来的2倍，高缩小到原来的 $\frac{1}{2}$ ，则圆柱的体积保持不变。（判断对错）

增加：在缺词处加一个漏字符号（∧），并在此符号下面写出该加的词。

删除：把多余的词用斜线（＼）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：⒈ 每处错误及其修改均仅限一词；

⒉ 只允许修改10处，多者（从第11处起）不计分。

    My uncle lives no far from my home and I visit him every Sunday. Yesterday I visited him with my sister by bikes. As usually, we stayed at his home for a very longer time. We talked about things that had been happened in my school last week, especially the low grades I had got. He encouraged me believe in myself but work harder. The talk with him really cheers me up. He also prepared a delicious meal for us. We three had the good time together. After leave his house, we rode home happily.

能源是人类社会活动的物质基础，其中常规能源有：____；____；天然气．清洁能源有____；____；风能等．

《永遇乐·京口北固亭怀古》感叹东吴那个强盛的局面，孙权那个英雄、风流余韵，都经历了无数的风雨，一去不返了，只留下京口供后人欣赏凭吊而已的句子是：____，____。