A batch job analyzes documents one at a time: each request has a unique 20,000-token document and a 300-token instruction, and no document is ever sent twice. Should you mark the document for prompt caching?

1. A Yes, since cached tokens cost about one tenth of normal input on every call.
2. B No, since cache writes cost extra and this prefix is never reread.
3. C Yes, since caching the document also reduces the cost of the generated output.
4. D No, since prompt caching only applies to prefixes of a few hundred tokens or less.