Topic selection isn't just a matter of saying "I'm going to write about X." It's important to start out with an idea of what you're going to write about along those lines, but it's also important to start your research with some flexibility in mind.
A lot of students tend to want to start the process of writing a paper by deciding what they are going to say and then trying to find articles to support that. A better way to go is to start with a general topic, do some initial exploratory research, refine the topic a little, do some more research, and so on.
This video from the North Carolina State University libraries provides an excellent overview of the process of selecting a topic: