Directions: In the following sentence, select the option that should replace the underlined phrase to make the sentence grammatically correct. If the sentence is correct as it is, select "No improvement required".

A large proportion of rural farmworkers suffer of chronic respiratory ailments due to prolonged exposure to dust.

The correct option to replace the underlined phrase is suffer from chronic respiratory.

Reasoning and Explanation:
1. Correct Preposition Usage: The verb "suffer" is followed by the preposition "from" when referring to illnesses, pain, or medical ailments (e.g., suffer from an allergy or suffer from ailments). The phrase "suffer of" is grammatically incorrect in standard English.
2. Adjective vs. Noun: The word modifying the noun "ailments" must be an adjective. "Respiratory" is an adjective meaning related to breathing or the lungs, whereas "respiration" is a noun. Therefore, "respiratory ailments" is grammatically sound, while "respiration ailments" is incorrect.
3. Corrected Sentence: "A large proportion of rural farmworkers suffer from chronic respiratory ailments due to prolonged exposure to dust."