Option 1 -> "Iron out" means to resolve or eliminate problems, difficulties, or discrepancies.
Option 2 -> "Iron in" is not a standard English phrasal verb.
Option 3 -> "Iron off" is not a standard English phrasal verb.
Option 4 -> "Iron on" refers to applying heat-transfer patches or labels, not resolving issues.
Hence, Option 1: iron out -> The phrasal verb "iron out" is used metaphorically (like smoothing wrinkles from fabric) to mean resolving or eliminating problems, inconsistencies, or discrepancies, making it the perfect fit for correcting errors in a report before submission -> correct