An Approval Process is the appropriate feature to manage and enforce that new vendors accept terms on agreements before an opportunity can be closed. This process can be configured to require approvals from designated approvers when certain conditions are met, ensuring that all necessary agreements are in place and validated before proceeding.
A: Email Alert cannot enforce acceptance of terms.
B: Dynamic Action primarily adjusts the user interface based on field values, not process management.
D: Validation Rule only validates data entry and cannot handle complex conditional approvals.
Reference: Approval Processes in Salesforce Documentation