One meaning of ‘an end’ is ‘a mental goal or purpose’; it is in this idiomatic context that the phrase has been used. But ‘such an end’ is slightly different. It gives a tone of a physical end which is not what is meant in the text. So E is better than C.
A, B and D or wrong because there is no proper single - word referent for those pronouns
GMAT Club Premium Membership - big benefits and savings