Since 'A' gives positive silver mirror test therefore, it must be an aldehyde or α -Hydroxyketone.
Reaction with semicarbazide indicates that A can be an aldehyde or ketone.
Reaction with OH− i.e., aldol condensation (by assuming alkali to be dilute) indicates that A is aldehyde as aldol reaction of ketones is reversible and carried out in special apparatus.
These indicate option (iii).

