岩栓的边缘通常是不露出的，因而不能确定其包裹的物质是什么。

The rim of the plugs is usually not exposed and the enveloping material cannot be ascertained.

youdao

岩栓的边缘通常是不露出的，因而不能确定其包裹的物质是什么。

The rim of the plugs is usually not exposed and the enveloping material cannot be ascertained.

youdao