参考答案

[A] owing to their undoubted and respectable status

【解析】事实细节题。根据题干关键词“monarchs”和“heads of state”，定位到第三段的最后一句话“...most royal families have survived because they allow voters to avoid the difficult search for a non-controversial but respected public figure.”(大多数的王室幸存下来是由于他们让选民可以避免去寻找一个不受争议且受尊敬的公众人物的困难)其中“non-controversial but respected public figure”正是A选项中“undoubted and respectable status”的同义置换。故A是正确答案。