The correct answer is D. no article.
The word "intelligent" is an adjective that describes a person's mental abilities. It is not a countable noun, so it does not require an article. The word "smart" is also an adjective, but it can be used as a noun to refer to a clever or intelligent person. In this case, it is being used as an adjective, so it does not require an article either.
The article "a" is used before singular countable nouns that refer to a specific person or thing. The article "the" is used before singular countable nouns that refer to a specific person or thing that has already been mentioned or is known to the listener. In this case, the reporting manager is not a specific person or thing, so neither article is necessary.
