Lungs clear to auscultation.

A) complete sentence
B) fragment
C) run-on
I say it is complete So A would be my answer.

fragment

DaKosha is right.

Your answer is correct. "Lungs clear to auscultation" is a complete sentence because it contains a subject ("lungs") and a predicate ("clear to auscultation"), which makes it grammatically complete. Well done!