A、A camera. B、A film. C、A photo. D、a picture. A信息明示题。文章第四段明确指出，a man’s mind is rather like a camera，由此可知，A正确。

Some people have very good memories, and can easily learn quite long poems by heart. There are other people who can only remember things when they have said them over and over.
    The famous English writer, Charles Dickens said that he could walk down any long street in London and then tell you the name of every shop he had passed. Many of the great men of the world have had wonderful memories.
    A good memory is a great help in learning a language. Everybody learns his own language by remembering what he hears when he is a small child, and some children seem to learn two languages almost as easily as one. In school, it is not so easy to learn a second language because the pupils have so little time for it, and they are busy with other subjects as well.
    A man’s mind is rather like a camera, but it takes photos not only 0f what we see but of what we feel, hear, smell and taste. When we take a real photo with a camera, there is much to do before the photo is finished and ready to show to our friends. In the same way, there is much work to be done before we can keep a picture forever in our minds. Memory is the diary that we all carry about with us.