this is a manhole cover, pretty common stuff and you will see it everywhere. But you connot ignore the danger behind it, especially for the kids, tell them that they cannot just step on it when walking on the road, because they might fall into it if they do.
    So tell your children, every time they see a manhole cover ahead on the ground, just walk around it.
    这是一个井盖，很常见的东西，你会在任何地方看到它。 但是你不能忽视它背后的危险，尤其是对孩子们来说，告诉他们他们在路上走路时不能随便踩它，因为如果他们这样做，他们可能会掉进去。
    所以告诉你的孩子，每次他们看到地上有一个井盖，就绕着它走。