Which sentence in the passage uses parallel structure?

A fashion trend not only changes but is also evolving. It grows and is sometimes defining the era in which it originated. In the 1950s, for example, wide-circle skirts and wearing long dresses were in fashion. Then in the 1960s, the A-line skirt and a miniskirt became trendy. Fashion forecasting involves predicting future trends by observing changes in the current situation and learning from the past trends.