The correct answer is D. no article.
The word “physically challenged” is a noun phrase that refers to people who have a physical disability. It is a general term that can refer to people with a wide range of disabilities, including mobility impairments, visual impairments, and hearing impairments.
In general, we do not use articles with general nouns. For example, we would say “I saw a dog” or “I saw the dog,” but we would not say “I saw a dog.” This is because general nouns refer to a class of things, not a specific thing.
In the case of “physically challenged,” we are referring to a class of people, not a specific person. Therefore, we do not use an article.
The other options are incorrect because they are all articles. A, an, and the are all articles that we use to refer to specific things. In this case, we are not referring to a specific thing, so we do not use an article.