OG12 第6题 关于them的指代 【求助】

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

答案选E，
为什么OG上说，C和D选项中“The pronoun them seems to refer to tourists,which is nonsensical”;而E选项中“and them clearly refers to chambers.”？
可以怎么判断出来？找了之前别人发的一些帖子，但还是没有弄明白，求教。

PS，有人说，
C句子结构：
The chambers were v.-ed, because tourists were v.-ing, which raise sth. in them...
them指代前面出现过的复数名词，前面有两个复数名词，一个chambers一个tourists，而且tourists还离得近点，有歧义。

E句子结构：
The chambers were v.-ed, because moisture ... had raised sth. in them...
them指代前面出现过的唯一的复数名词，chambers，无歧义。by tourists出现在修饰moisture的定语中，不可能做them的antecedent。

但是E和D还是很相似呀