求翻译：我认为，欧洲主权债务危机的爆发，固然是由于其国家财政货币政策的不合理，经济福利政策安排不完善等内在原因促成的，但是美国三大评级机构一再地下调其等级，无疑也起到了推波助澜的作用。在希腊债务危机发展恶化的过程中，信用降级导致危机升级，危机升级又使信用评级进一步下降的恶性循环表现得非常明显。是什么意思？

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I believed, European sovereignty debt crisis eruption, no doubt is because its national finance monetary policy is unreasonable, the economical welfare policy arrangement imperfect and so on the intrinsic reason facilitates, but the American three big rating organizations decline its rank repeatedly

I believe that Europe's sovereign-debt crisis broke out, is, of course, because of their national fiscal and monetary policy is unreasonable, economic welfare policy arrangements are not perfect, and other causes, but the United States three largest rating agencies repeatedly downgraded its rating,