When a Lead is converted into an Account, Contact, and Opportunity, standard fields are mapped automatically. However, custom fields require manual configuration to ensure d3ata flows through the conversion process. First, the Platform Administrator must create a corresponding custom picklist field on the Contact object (Option B) with the same values as the Lead field. Second, the administrator must go to the Lead Object Manager, select "Fields & Relationships," and click Map Lead Fields (Option C). Here, the admin explicitly maps the Lead custom picklist to the newly created Contact custom picklist. Without this mapping, the data will be lost during conversion.
Validation rules (Option A) and making the field required (Option D) ensure data exists on the Lead but do not facilitate the transfer of that data to the Contact.