1. I AM WRITING in connection with the advertisement which APPEARED on 12 April. (Present Continuous; Past Simple)
2. I originally STUDIED chemistry at university. I GRADUATED with a first-class degree. (Past Simple).
3. I now COMPLETED a postgraduate degree in administration. (Past Simple)
4. I HAVE BEEN TRYING to find a permanent job for a considerable time. (Present Perfect Continuous)
5. Indeed, I HAVE already WORKED for several companies on a temporary basis. (Present Perfect)
6. In my first job, I WAS responsible for marketing. (Past Simple)