Say that you are worried about the following things.
whether: -lkka or -ŭlkka
That teacher will come (to a party).
선생님이 파티에 올까 걱정해요.
That there won’t be enough food.
음식이 모자랄까 걱정해요.
That Mr. Kim might not come.
김선생님이 않 오실까(봐) 걱정해요.
That your girlfriend might not like you any more.
여자 친구가 저를 않 좋아 할까(봐) 걱정해요.
That it might rain.
비가 올까(봐) 걱정해요.