“指代”问题求解！

xiaobaibai92112

In late 1997, the chambers inside the pyramid of the Pharaoh Menkaure at Giza were closed to visitors for cleaning and repair due to moisture exhaled bv tourists, which raised its humidity to such levels so that salt from the stone was crystallizing and fungus was growing on the walls.
(A) due to moisture exhaled by tourists, which raised its humidity to such levels so that salt from the stone was crystallizing
(B) due to moisture that tourists had exhaled, thereby raising its humidity to such levels that salt from the stone would crystallize
(C) because tourists were exhaling moisture, which had raised the humidity within them to levels such that salt from the stone would crystallize
(D) because of moisture that was exhaled by tourists raising the humidity within them to levels so high as to make the salt from the stone crystallize
(E) because moisture exhaled by tourists had raised the humidity within them to such levels that salt from the stone was crystallizing

正确选项为E，为什么CD中的them就被判定为ambiguous，指代的是tourists，而E中的就是clearly指代walls 呢？
求大神解答！

chantal891121

them指代的是chambers
E是因为在because从句中主语是moisture，是单数，而代词优先指代句子主语，tourists只是定语中的状语，级别太低，基本指不到它
C中tourists是从句中的主语，肯定是优先指代的对象
D，个人觉得说模糊指代有点牵强，猜测可能是因为because of moisture 作为状语存在，相对于because从句，可能与主句的紧密程度不高，所以them就指代了moisture定语从句里的复数名词了，解释的也有点牵强，sorry。。

xiaobaibai92112

chantal891121 发表于 2014-8-12 01:01
them指代的是chambers
E是因为在because从句中主语是moisture，是单数，而代词优先指代句子主语，tourists ...

谢谢！
这道题是挺纠结的。。。