What carrier is SBD?

Could you please clarify what you mean by "SBD" in the context of "What carrier is SBD?"? Are you referring to a specific type of cryptocurrency, a company, or perhaps a technology acronym? If it's a cryptocurrency, SBD is typically associated with Steem Dollars, which is a token within the Steem blockchain ecosystem. It's not a traditional carrier in the sense of a telecommunications provider or a shipping company. Could you provide more context or elaborate on your question to help me give a more accurate and relevant answer?