6. 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 by
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
楼上说的是不错的 代词指代本身有倾向性
对于E而言，them实际上书在 A, because B这句话里面，所以them优先指代了主句主语chambers
而对于D them 在一个that定于从句里面 所以这个them会去指这个从句里面的主语 指不了就去找附近的复数名词
对于C them在which从句里面 而which从句是前面because从句的从句，然后就优先指到了tourists了
