需要牢记的是，在做这个测试时，你必须保证你的钻石是完全干净且没有沾染油污或灰尘。

Keep in mind, though, for this test work, you must make sure that your diamond is completely clean and free from oil or dirt.

youdao

需要牢记的是，在做这个测试时，你必须保证你的钻石是完全干净且没有沾染油污或灰尘。

Keep in mind, though, for this test work, you must make sure that your diamond is completely clean and free from oil or dirt.

youdao