A stakeholder is a person or group:

 Definition of a Stakeholder:

Stakeholders include anyone with an interest in the success or failure of a project or initiative, irrespective of their direct financial involvement or usage of the system.

 Why Other Options Are Incorrect:

B. Vested in success and tied to budget: Budget involvement is not a prerequisite for being a stakeholder.

C. That has budget authority: Stakeholders are not limited to those with financial control.

D. That will ultimately use the system: Users are stakeholders, but stakeholders are not limited to end-users.

 EC-Council CISO Reference:

EC-Council defines stakeholders broadly to include all parties affected by or invested in a project's outcome, emphasizing their influence and varied roles.