点解下水道的盖是圆形的？

Why are manhole cover round in shape?

youdao

下水道出入孔：一种常带有盖的孔道，人可以由此孔进出排道、锅炉、下水管或类似设施。

A hole, usually with a cover, through which a person may enter a sewer, boiler, drain, or similar structure.

youdao

今天我坐摩的的时候翻车了，后背摔在一个没盖盖子的下水道上。

Today, I was taking a motorcycle taxi, when we lost balance and toppled over. I fell on my back on an open sewer.

youdao