A、In the late 1970s. B、In the early 1970s. C、During World War II. D、In the late 1960s. A新闻提到。养老金制度在第二次世界大战时开始流行，到了20世纪70年代末达到流行高

The number of Americans over the age of 65 is expected to double between now and 2030. This next generation of retirees will be the healthiest, best educated, and most wealthy in American history. But many of them won’t have a retirement benefit their parents’ generation fought hard to get It is something known as a defined-benefit plan, or "pension". Retired workers who have a pension continue to be paid a certain percentage of their highest annual salary—usually anywhere from one to three percent—multiplied by the number of years they worked for the company. Pensions first became popular during World War II, when a federally-approved wage-freeze meant unions had to negotiate for retirement benefits, instead of pay increases. Pensions reached the height of their popularity in the late 1970s, when more than 60 percent of Americans had one.
    1. What problem does the next generation of retirees have?
    2. When did pensions reach the height of their popularity?