"Who fed cheese to the dog?"
Translation:누가 개에게 치즈를 먹였어?
Many of these are causatives. Feed = make eat.
Some are real passive forms. 안다 = to hug; 안기다 = to be hugged.
You can also have a passive causative, like to be fed.
There are some other forms, where I have been memorizing sentences without understanding how to make more like them.
It is unfortunate that there are no hints for this lesson to explain these different forms.