Periods of inflation and deflati

Periods of inflation and deflation had 【alternated】 for generations.
A、altered
B、merged
C、become different
D、happenedby turns
【正确答案】：D
【题目解析】：句意：通货膨胀与通货紧缩的时期已经轮流交替了好几代。alternate在句中的意思是“交替,沦流”。选项中alter意为“改变”；merge意为“合并”；become different意为“变得不同”；happen by turns意为“轮流发生”。故本题选D。