bp Project Management Graduate interview questions

Application form, online tests, phone interview with HR, Skype interview with someone from your future department and finally assessment centre. I got until the Skype interview which is a bit hard. They present real cases and ask you to apply project management into those cases to give your opinion. I answered with my knowledge from university but I was told that although I clearly knew the theory, I showed little experience (maybe that's why I was applying for graduate position).