Except during an emergency, under what circumstances can a pilot expect landing priority?

Answer: C — In turn, on a first-come, first-serve basis.

A pilot can expect landing priority under the circumstance of being low on fuel. This situation often denotes an urgent need to land, and Air Traffic Control (ATC) recognizes the critical nature of fuel status. While other scenarios may have their own merit, the safest operational protocol is to prioritize those aircraft that are in a potentially dangerous position regarding their fuel reserves. Considering the other choices, being cleared for an IFR approach generally does not imply priority but establishes a planned approach path, large, heavy aircraft may require special handling but do not inherently have priority, and the idea of first-come, first-served implies a simplistic approach which does not adequately account for urgency or safety factors such as fuel levels. Hence, priority is more influenced by a critical need rather than merely sequential entry.