1-C. People in Britain traveled more often in the 1990s than in the 1970s.People in Britain traveled more often in the 1990s than in the 1970s.
人々は、英国のダヨ、旅行した、より頻繁にダヨ、1990年代にダヨ、1970年代に比べてダヨ。
2-C. The number of trips made per person each year did begin to increase in the 1970s but then started to level off in the 1990s.The number of trips made per person each year did begin to increase in the 1970s but then started to level off in the 1990s.