Sentence Correction

LOL . GmatGuruNy . This is very subtle . Do we have to analyse each sc so closely on test day too. I still cant help chuckling at the way they hid the error

GMATGuruNY wrote:

mundasingh123 wrote:Hi GmatGuruNY , substituting D in the sentence we get
The scientists noted that rats suffering from the rare degenerative disease had begun to die six months earlier without any signs of the disease shown then

But the dsease is the not the subject of the sentence
Disease is a part of a prepositional phrase which is part of another noun modifier
So basically cant we leave out the whole modifier
The scientists noted that rats had begun to die six months earlier without any signs of the disease shown then

also how does The modifier "without ... " modify "disease " when the two are so distant from each other. I am totally confused . The prepositional phrase is closer to the verb so why cant the "without ... " modify the verb

Yes, entire phrase (without...then) modifies die. How did the rats die? Without any signs. But within this modifying phrase, SHOWN (an adjective) seems to modify DISEASE, the noun that it follows. The result: the modifying phrase seems to be saying that DISEASE was SHOWN, but the rats died WITHOUT ANY SIGNS of it. The following would be better:

The rats died without showing any signs of disease.

Hi! In this particular question I was stuck between A and E. I chose E assuming that 'it' refers to the disease because the other nouns - rats and scientists - are both plural, and that 'them' refers to rats as both are in object position.
I rejected A because I thought 'they' could refer to either scientists or rats.
Can anyone please help me understand how 'they' in option A is not ambiguous and pronouns in option E are?.
Thanks in advance !