The correct option is orchestrator.

An orchestrator function defines and coordinates the overall workflow and enforces the order of steps. An orchestrator calls other functions to perform work and it can wait for long running operations by using durable timers or external events so it can handle a credit verification that takes up to four days without tying up a compute thread.

The orchestration is deterministic so the long running or blocking work itself should run in worker functions, while the orchestrator manages retries, sequencing, and durable waiting across the entire loan approval process.

client is incorrect because the client is merely the starter or caller that triggers an orchestration and it does not coordinate the ordered steps of a workflow.

activity is incorrect because activity functions perform the discrete work units such as calling a credit bureau, and they should not be used to control or wait for the overall workflow for days.

entity is incorrect because entity functions model small stateful objects and are not intended to orchestrate a multi step, ordered workflow across long running operations.

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