staining smear examination

例句：

1. 1.The stain on the shirt is from the coffee spilled on it.
   衬衫上的污渍是咖啡溅上去的。
2. 2. The scientist used a staining agent to detect the presence of bacteria in the sample.
   科学家使用染色剂来检测样本中细菌的存在。
3. 3. The stain on the carpet was caused by the spilled red wine.
   地毯上的污渍是由洒落的红酒造成的。