How do you retry a failing activity function with exponential backoff in Durable Functions?

1. A Wrap the call in a try/catch loop
2. ✓ B Call it with a RetryOptions instance specifying first retry interval, backoff coefficient, and max attempts (correct answer)
3. C Configure retries in host.json only
4. D Use a Timer trigger

Shortcut: CallActivityWithRetryAsync accepts RetryOptions, and the Durable framework persists retry state so backoff survives host restarts.