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题库 / Prep2007E1-SC-115
Many population studies have linked a high-salt diet to high rates of hypertension and shown that in societies where they consume little salt, their blood pressure typically does not rise with age.
shown that in societies where they consume little salt, their
shown that in societies that have consumed little salt, their
shown that in societies where little salt is consumed,
they showed that in societies where little salt is consumed,
they showed that in societies where they consume little salt, their
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仔细想了下D的问题，they的指代没什么问题，按逻辑意思最合理的对象进行指代即指Many population studies；
and 前后也不一定要求时态平行，但这里确实是时态的问题，现在完成时表达事情发生在过去,并一直持续到现在,且过去发生的动作对现在有一定影响，而一般过去时则表达过去某一段时间的事情，和现在没什么关系即现在不一定这样。再来看句子，and前后几乎说的是相同内容的事情，即高盐饮食和高血压有联系，那么前面用现在完成时后面用一般过去时自然是不合理。
然后就算是改为they have shown，就是赘余的问题了
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