as, an, for

"An" is used before singular nouns that begin with a vowel sound to avoid a jarring transition between words.

In this context, "for" is the correct preposition to indicate employment.

"An" is used before a noun starting with a vowel sound, as in "an elegant dress."

"For" is used to indicate the reason or purpose for which someone is known.

"For" is used to indicate the organization or entity one works for.

"As" is used to describe how something is done, in this case, singing.

"For" is used to indicate the purpose of the action, which is getting groceries in this case.

"For" is used to specify the reason or cause for recognition.

"An" is used before a noun starting with a vowel sound, such as "an unusual necklace."

"For" is used to indicate the reason for someone's reputation or recognition.

Use "for" to indicate someone's skill or talent in a specific area, like "talent for painting."

"For" is used to indicate the reason for someone's recognition, in this case, kindness.

Use "in" to indicate someone's interest or involvement in a particular field, like "interest in photography."

"As" is used to denote someone's role or identity, as in "recognized as an expert."

"For" is used to indicate the entity or organization someone worked on behalf of.

"As" is used to indicate the role or character portrayed, as in "acted as the lead role."

"In" is used to specify the field of study, like "studying in medicine."

"For" is used to indicate the reason or quality for which someone is admired, in this case, dedication.

"In" is used to express one's passion or interest in a particular field, such as "passion in writing poetry."

"In" is used to denote someone's talent or skill in a specific domain, like "talented in playing the piano."