In DMF index, F indicates a tooth with:
Indicates the number of permanent teeth that have been attacked by caries, but which have been restored to keep them in a healthy condition in mouth. 
A tooth may have several fillings, but it is counted as one tooth. 
If a tooth has a filling but shows evidence of recurrent decay, it is counted as a decayed tooth. (Option 3 is eliminated) 
Temporary restorations are considered as Decayed (Option 1 is eliminated)
Only permanent teeth are considered (Option 4 is eliminated).

Essentials of preventive and community dentistry
5th edition
Soben Peter
Zinc oxide eugenol filling
Silver amalgam filling
Caries below an existing restoration
Permanent filling in a deciduous tooth