Alkyl Halides (Halogenoalkanes)

Correct Option: D
Option A Explained: Incorrect. The locant numbers are right, but substituents must be written in alphabetical order, so ethyl should come before iodo.
Option B Explained: Incorrect. When both directions give the same set of numbers (3,5), the substituent coming first alphabetically gets the smaller number; ethyl comes before iodo.
Option C Explained: Incorrect. The substituents are written alphabetically, but ethyl should get number 3, not 5, because it comes before iodo alphabetically.
Option D Explained: Correct. Alkyl groups and halogens are treated equally, and in a numbering tie, alphabetical order is used, so ethyl gets 3 and iodo gets 5.