In Option A - INCORRECT.
Aside this statement been a repetition of the stated question, it is wrong due to the use of ''the'' as a determinant of the word older people. Since there is both'' which serves as a conjunction to identify the two words then the need of ''the'' is not needed.

In Option B - INCORRECT.
This sentence formation is wrong. ''both younger people and the other people''. ''Both'' already qualifies the two people but now there is a separation with the use of ''the'', and a repetition of ''people'' making the sentence unreasonable.

In Option C - INCORRECT.
There is a repetition of ''The and people'' which is not needed, cos it serves as a tautology in the sentence.

In Option D - CORRECT
This statement sounds correct and has the right sentence formation ''both younger and older people''

In Option E - INCORRECT.
In this sentence there is too much explanation on people who are involved. And this makes the sentence too complex to understand. The use of ''both '' already specified that there are two people involved, now the use of ''who and those'' again?. The sentence formation is apparently wrong.