His father said, "Why can't you admit the truth? "
Answers
His father asked him why he couldn't admit the truth
Indirect/Reported Speech refers to a dialogue being told to a third person/reporting what happened to a third person.
Example: Kendall said,"I'm going in." (Direct)
Kendall said that she was going in. (Indirect)
In the above example, when writing in indirect/reported form, the sentence changes according to its tense. Also, modifications regarding certain words like 'this' changes to 'that', 'tomorrow' changes to 'the next day', 'will' changes to 'would', 'can' changes to 'could' and many other words have to be made. Also, if the sentence is contains an interrogation, then 'said' changes to 'asked'. Punctuation marks other than a full stop (.) cannot be used in indirect/reported speech.
His father said,"Why can't you admit the truth?" (Direct)
His father asked why he couldn't admit the truth. (Indirect)