Hint:First we must read all the given options and we must know the usage of the words. Later we must know the usage of the different words. Choose the option which will be grammatically correct. Also we must see that the selected option will make the sentence meaningful.
Complete step-by-step answer:
Now let’s examine and understand all the above given options.
Rich: As per question point of view we need to use nouns in the given sentence but ‘Rich’, it is an adjective here which is not suitable for the sentence. So it is an inappropriate option for the given sentence.
Riches: ‘Riches’ is a noun which shows ‘material wealth’ but according to the question people can help the poor not material. So it is also an inappropriate option for the given sentence.
A rich: This is a noun but article ‘A’ is not appropriate here because it is showing a singular subject and according to the question all rich people should help the poor not only one that’s why this is also an inappropriate option for the given sentence.
The rich: ‘Rich ‘is an adjective but after adding article ‘The’ it has become a noun and ‘The rich’ is also showing a group of people so according to the question ‘The rich’ is a perfect and an appropriate option.
So the correct answer will be option [D].
Note:Articles are the words like “A, An, The” which combine with a noun to form a noun phrase.
Noun- Noun is a word that refers to a specific or many objects.
Adjective- Adjective is a word which helps in modifying a noun or a noun phrase.