what is the passive of this sentence:

[لطيف]

the sentence has no passive at all because it has already had v. to be and i think it is a really tough joke from the teacher writing this kind of sentences and most of the answers are not correct thats because our dear teachers are looking for the an aswer without knowing that the sentence itself can't be changed into passive but if you want the answer it is all right
I'm frightened of dogs
I'm scared of dogs
I'm trified of dogs