7. 下列哪个不是重力滑动构造要素…………（ ）

A．The World War I had many European countries suspend convertibility of their currencies into golDB．The political costs of maintaining the overvalued pound were so great in the United Kingdom ．C．Nations facing 1929 – 1933 worldwide recession decided to pursue objectives such as higher employment rates and real growth rates, rather than to maintain the exchange value of their currencies．D．All of the above are the reasons that the gold standard finally collapseD．

A、Geological cycle
B、Long time cycle
C、Biological cycle
D、Opened cycle