Choose the right option.
People have much greater freedom in choosing a job than people(have/had/have had/had had) one hundred years ago. It also (became/is becoming/will have become/had become) more common for people in the US to make major career changes at some time during their lives. In fact by the time the average person retires,it is not unlikely that he or she 3(changes/will be changing/is changing/will havw change) careers at least once

had, is also becoming, will have changed