In Colorado, earnest money must be deposited:

Option A is incorrect because Colorado does not have a 10-day statutory requirement for earnest money deposit. While some states may impose specific timeframes, Colorado allows the contract to govern this timing requirement.

Option C is incorrect because earnest money is typically deposited early in the transaction, not at closing. Depositing at closing would defeat the purpose of demonstrating good faith and could impact the enforceability of the contract.

Option D is incorrect because while Colorado doesn't mandate a specific timeframe, contracts almost always include earnest money deposit provisions, creating a requirement based on the contractual agreement.