"it" - it cannot refer to a phrase like in this example. "It" cannot refer to bunch of words. its too much to ask. "It" can only refer to a clear noun. Hence A is suspicious.
"that" - when you see two "that" - Immediately suspect "that".
split "has devoted" / devoted - B and D gone. u need simple past tense. A, C and E remain.
A has "it" - ambiguous
C has "such as" - in gmat "such as" is used to include examples. Not here. Cross it and move on !
E remains. that has to be the answer since others are wrong one way or the other.
A is wrong becos the pronoun 'it' has no proper antecedent( so also 'that' in B and D) To such an end in C is wrong idiom. E remains. to that end is the right idiomatic way.
His determination was to find the site of troy and he dedicated his career to do it. what's so wrong here?
'to that end' doesnt somehow fits in the this sentence.
Please elaborate. and if you have some other examples on the similar lines, it would be really helpfull if you can post them here, just as an example.