Andrew Initially Worked with a Travel Website for Few Months

Andrew initially worked with a travel website for few months and then became self-employed by starting a martial arts school,where he taught karate to teenagers.After an year,he closed the school and joined an advertising firm.After two years,he quit the advertising firm and became self-employed as a freelance music composer.Which of the following terms indicates the changes in Andrew's employment structure?

A) Volatility
B) Adverse possession
C) Pop-up business
D) Easement