Social Recall helps people with prosopagnosia by ______.

参考解析：

细节理解题。根据文章最后一段第二至四句“To use this app, a person first receives an image of someone’s face, from either the smartphone s camera or a photograph, and then tags it with a name. When the camera spots or recognizes that same face in real life, the previously entered information is displayed. The collected data are stored only on a user’s phone, according to the team behind the app.”可知，用户使用智能手机的摄像头或照片中获取某人的面部图像，然后给它加上一个名字。当摄像机在现实生活中发现相同的人脸时，就会显示之前输入的信息，从而帮助脸盲症患者识别此人的信息。故选D。