The correct answer is: D. no article
The article “a” or “an” is used before singular nouns that refer to a general or unspecified thing. In this case, the speaker is referring to a specific career path, so the article “a” or “an” would not be appropriate. The article “the” is used before singular nouns that refer to a specific or unique thing. In this case, the speaker is not referring to a specific eye surgeon, so the article “the” would not be appropriate.
Without an article, the noun “eye surgeon” is understood to be a general term for someone who specializes in surgery on the eyes.