Questions & Answers about El chico me intimidó y yo no sabía qué responder.
Why does the indirect question use the infinitive responder instead of a conjugated verb?
When the subject of the main clause and the indirect question are the same, Spanish prefers the infinitive. Since you are the one who didn't know and you are also the one who would answer, you use qué responder. If the subjects were different, for example if you didn't know what the boy would answer, you would need a conjugated verb like qué respondería.
Why does qué have an accent mark if there are no question marks?
Interrogative words always keep their accent marks in indirect questions. Even though it is embedded in a statement, the word qué still functions as a question word asking what to answer.
Why do we use the preterite for intimidó but the imperfect for sabía?