Concept:The correct word must describe purposes that are proper and justifiable for spending public money.
Explanation:"Legitimate" means lawful, valid, or justifiable, which fits the idea of acceptable use of public funds.
"Discreet" means careful or secretive, so it does not suit "purposes."
"Legal" relates to what is allowed by law, but "legitimate" is the more natural and common choice for this meaning.
"Executive" refers to managing or administering, so it is not appropriate here.
Therefore, the sentence reads correctly as: "Public money should be used only for legitimate purposes."
Answer:A. legitimate