Read the passage and answer the questions A and B.

Dreams have fascinated philosophers for thousands of years, but only recently have dreams been subjected to empirical research and scientific study. Chances are that you've often found yourself puzzling over the content of a dream, or perhaps you've wondered why you dream at all. First, let's start by answering a basic question: What is a dream? A dream can include any of the images, thoughts and emotions that are experienced during sleep. Dreams can be extraordinarily vivid or very vague; filled with joyful emotions or frightening images; focused and understandable or unclear and confusing. Why do we dream? What purpose do dreams serve? While many theories have been proposed about the reason and function of dreams, no consensus has emerged. Considering the time we spend in a dreaming state, the fact that researchers do not yet understand the purpose of dreams may seem baffling. However, it is important to consider that science is still unraveling the exact purpose and function of sleep itself. Some researchers suggest that dreams serve no real purpose, while others believe that dreaming is essential to mental, emotional and physical well-being. Next, let's learn more about some of the most prominent dream theories. Consistent with the psychoanalytic perspective, Sigmund Freud's theory of dreams suggests that dreams are a representation of subconscious desires, thoughts and motivations. According to Freud, people are driven by aggressive and sexual instincts that are repressed from conscious awareness. While these thoughts are not consciously expressed, they find their way into our awareness via dreams. In his famous book The Interpretation of Dreams (1899), Freud wrote that dreams are "--- disguised fulfillments of repressed wishes.