4. What makes you qualified for this particular job?
Again, explain that you are very interested in the job and demonstrate what it is about your past experiences, education and qualifications that makes you ideal for the job. Show enthusiasm and support your answers with evidence wherever you can (eg. my summer internship at Citibank gave me broad exposure to the area of equity analysis and I think I can apply many of the tools I learnt there in this job). Elaborate on all the past experiences and skill sets that make you suitable for the job. In cases where your past experience is not directly relevant, you can still find elements of it that can be useful. Play up team skills, computer skills, leadership roles, specific courses and independent research activities that can be useful to the job at hand to show your initiative even where you don't have directly relevant job experience.
5. What can you do for us that someone else can't?
Demonstrate key strengths, skills and personal characteristics.
6. Why should we hire you?
See 3. Because you have all the experience/ traits/ credentials demonstrated in 3 and in addition to being qualified, you are enthusiastic, intelligent, hardworking, flexible and willing to learn. Also mention any key relationships you may have that may assist you in the job.