因为photo是photograph的简写，复数是photographs，简写是photos。以o结尾的名词，变复数时：1、加s，如：piano---pianos钢琴；2、加es，如：potato--potatoes西红柿。
photograph双语例句
1.She was clutching a photograph.
她紧紧抓着一张照片。
2.Several papers carry the photograph of Mr Anderson.
好几家报纸刊登了安德森先生的照片。
3.The photograph was taken on a very wet,dull day.
这张照片拍摄时下着雨，天色阴沉。
4.Few details could be distinguished on the photograph.
照片上几乎看不清任何细节。
5.a developing photograph placed in a bath of fixer
在显影罐中冲洗的相片