polymictic lake

例句：

1. 1. The soil isvery porous, allowing water to penetrateeasily.
   土壤非常多孔，水可以很容易地渗透。
2. 2. Polymictic lakes arecommon in the desert regions ofthe world.
   多孔湖在世界上干旱地区很常见。
3. 3. The rock is porous, allowing gases to escape quickly.
   这块岩石是多孔的，气体可以很快地逸出。