Cloud Service Partner is correct because the third party document storage vendor is collaborating with a major cloud platform to deliver services in regions where it lacks its own data centers.

A Cloud Service Partner typically extends a cloud platform's reach by providing software, delivery, regional presence, or channel services that complement the platform. The partner works with the platform to deliver solutions in locations where the partner or the platform alone might not have presence, and the relationship focuses on joint delivery and go to market activities.

Cloud Service Broker is incorrect. A broker intermediates between providers and customers to aggregate, integrate, or manage services and it does not usually describe a vendor teaming with a platform to extend regional delivery in the way a partner does.

Cloud Service Customer (CSC) is incorrect. A customer consumes and pays for cloud services rather than forming a collaborative arrangement to deliver services on the provider's regional footprint.

Cloud Service Provider (CSP) is incorrect. A provider owns or operates the underlying cloud infrastructure and offers it as a service. In this scenario the document storage vendor is leveraging the platform rather than operating the global infrastructure itself, so the vendor is a partner rather than the provider.

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