Which conditions best capture Muslim’s criterion in this concluding discussion?

Historical Examples of Muʿanʿan Transmission and the Conclusion of Muslim’s Introduction

• Any two named narrators automatically yield a sound chain
• Reliable non-mudallis transmitters, genuinely possible contact, and no evidence of disconnection
• A written record of the exact hearing session for every ʿan-report
• Contact is possible even where narrators are unknown, so the chain is accepted