Final answer:
The sentence with a misplaced modifier is option 1) He only talks about changing his habits.
Step-by-step explanation:
In this sentence, the modifier 'only' is misplaced. It should be placed directly before the verb it is modifying, which is 'talks'. The correct sentence should be 'He talks only about changing his habits'. A misplaced modifier occurs when a word or phrase is separated from the word it is modifying, causing confusion or ambiguity in the sentence.