We do say "Jack was afraid of XXX".
In your question, "what" asks about those possible things.
Student or Learner
Jack was afraid > what was he afraid "of"
why do we use "of"?
we don't say "Jack was afraid of"
I don't know really
and "what was he afraid" is it correct sentence?
Please help me teachers
>we don't say "Jack was afraid of"
You're correct. We don't say "Jack was afraid of" by itself. But we do say "What is Jack afraid of?" by itself.
"What is he afraid?" doesn't make sense. "What makes Jack afraid?" is a good sentence, and is similar to "What is Jack afraid of?" = "Of what is Jack afraid?"
We use prepositional phrases often after many adjectives and verbs: "I am tired [of waiting]"; "I am searching [for an answer]".
The question form needs a preposition if the whole sentence uses a preposition: "What are you tired of?"; "What are you searching for?".
If there is no preposition in the answer question, "I am seeking happiness", then there's no preposition in the question: "What are you seeking?"