For this one you're looking to identify what the images are about and what they are trying to convey - what is the meaning and the message within the image/images?
If you're accessing the right kind of sources for your research - journals such as the British Journal of Photography or books, the chances are you're going to be able to get a sense of the meaning behind the images because you're looking at research material where this aspect of the photography is discussed and identified.
When you're looking at images some of the key questions you need to be asking is what are these images about and what are the images trying convey? It's easy to identify what they're of, but the deeper questions are more complex and difficult to identify what the meaning is.
The process you should adopt should be one of initially offering a suggestion as to what the images could be about. But, then you must do the research and look for reviews and interviews and try and ascertain the facts. Generally in interviews the photographer will be asked about and will explain the meaning behind the images. Another good source for such information is the photographers own websites. Look for the specific body of work or series of images and they'll be accompanied by an introduction and explanation to the work. Look also for links to reviews on the photographers website, have a look through these too.