Final answer:
The subject of the sentence is Gabriel and no change is necessary in the sentence.
Step-by-step explanation:
In the given sentence, the subject is Gabriel. The verb is 'looked' and the complement is 'as if he had sat in a puddle of bleach.' The clause 'as if he had sat in a puddle of bleach' is an adverbial clause modifying the verb 'looked.' Therefore, no change is necessary in the sentence.
Learn more about Subject of the sentence