The context of the sentence clearly points to option (a) being the only sensible and appropriate fit. Although, all the other option are grammatically correct, they fail to fit the context.
Consideration: Careful thought or deliberation; also, something given (e.g., payment) in exchange for something else, often in a legal context.
Purpose: The reason or intention behind an action or existence; a goal or aim.
Proposal: A plan or suggestion put forward for consideration or discussion; also, an offer of marriage.
Circulation: The act of moving or flowing (e.g., blood, currency); also, the distribution or spread of something (e.g., information, publications).
Agreement: A mutual understanding or arrangement between parties; also, harmony or consistency in opinion or action.
Hence, the correct answer is option (a).
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