Topic: Group verb,

Best Answer Explained in Below-:

The phrase "put up at" is commonly used in English to describe the act of staying or lodging at a particular place, especially when referring to accommodations such as hotels or inns. In this context, the original sentence states, "When it was morning they decided to put at an in," which suggests the characters are considering where to stay overnight. The correct phrase, "put up at," implies their decision to settle into an inn for rest or shelter as day breaks.

The other options do not convey the same meaning:

- **A) Put out in** does not make sense in this context, as it suggests taking something outside or away.
- **B) Put off at** implies a delay or to defer action, which does not fit with the idea of deciding on a place to stay.
- **C) Put at** lacks a specific or commonly understood meaning in reference to accommodations.

Therefore, "put up at" is the most appropriate choice, indicating their intent to find lodging for the night. This phrase is idiomatic and conveys the intended message clearly in the context provided.