"Why are you applying for a job that you didn't major in?"
"Why didn't you pursue a career in your major?"
In the United States the statistics for a person changing career paths is very high. It's something like an average person will change careers five times. Changing jobs is one thing, but completely changing careers is a big move. So this question is not that significant. If everyone worked in the industry as their major, then this question is more important, but because everyone changes jobs frequently, it's no big deal. You just have to use this opportunity to show them how much you like the current industry you are in.
Short Answers
"I majored in English because I liked to write. Because I didn't know exactly what I wanted to do, I majored in something I was very interested in. After working for a year on the marketing team, I realized that this is what I want to be doing."
"I majored in History, but during my senior year, I had an opportunity to work at an accounting firm. After seeing first hand at the work they were doing, I really wanted to become an accountant."
"I was planning on going to Dental School so I majored in Biology. After working with computers, I realized how interesting and challenging it was. So I studied computers on the side because I wanted a career working with computers."
Long Answer
"I enjoyed majoring in psychology, but I didn't want to become a psychologist. I just found the subject to be very interesting. It also helped me to understand a wide variety of things. For my career, I wanted to be doing something I was good at and what I enjoyed doing. I had an opportunity to work at a smaller logistics company as an administrative assistant. During that time period they were short handed and I actually got to do some planning and organizing for one of the smaller clients. I didn't lead anything, but I realized how much I enjoyed the work. Ever since then, I've been studying up on planning, logistics, and business."
This example does three things. It explains why this person is not going into a field related to their major, it is explaining why this person is going into logistics, and finally it is showing passion for the industry and a desire to learn. Since you are probably competing against people who majored in logistics, you need to make an impression with your answer. So you should definitely show enthusiasm here.