💡 Detailed Explanation
The correct choice is 'られ' (passive indicator for Group 2 or Group 1 verbs). The verb '吠える' (hoeru - to bark) is Group 2, and conjugates to its passive form '吠えられる' (hoerareru) in the te-form '吠えられて'. This is an adversity passive, showing the speaker was negatively affected by the dog's barking. Sentence translation: 'Last night, I was barked at by the dog in the next room and couldn't sleep.' 'させ' indicates causative.