The solution to this particular question should come easy as it does not have much emphasis. So, let's do justice to it below<i class="em em-blush"></i>

First, solution comes in OPTION A - INCORRECT, the repetition of "one who" is clearly not required in this sentence because it does not offer any support or meaning to the statement. In actual fact, it is very inappropriate to lift the answer from the question so asked.

Here in OPTION B - INCORRECT, we all know there are numerous people there, so, there should not be any need to emphasis by using the word "them". However, we need to recognize its place as a pronoun used in place of the noun. It is still a wrong choice of option.

Here, in OPTION C - INCORRECT, we have a case of an unnecessary use of a connector in the form of "and". The comma sign used in the statement has definitely separated the sentence into its component parts so there should not be any need for the use of "and" again.

In this OPTION D - CORRECT ANSWER, our attention should be on the use of an apt, appropriate and fitting pronoun. In this case "whom" has been used quite suitably to the contextual meaning of the statement.

In OPTION E - INCORRECT, we have an erroneous use of pronoun. The word "which" should be used for inanimate objects and not living ones. It does not entails nor does it dignify the human specified in the article.