Last night it snowed heavy. When Susan and I got up in this morning, we found the whole garden was covered with thick snow. So we decided clear the path. We got two spades but began our work at once. We both worked so hard that the path was clear soon. Seen this, our father felt very surprising. He smiled happily at us, telling us that we have done a good job and that he was proud for us. Finally Father gave us some pocket money as a reward for the Spring Festival. Susan and I was happy because we had all got the money through labor.

遇有下列情况之一时，预计雷击次数大于或等于0.06次/a的一般性工业建筑物；在平均雷暴日小于或等于15d/a的地区，高度在20m及以上的烟囱、水塔等孤立的高耸建筑物应划那一类防雷建筑物？