Select the option that expresses the given sentence in indirect speech.
"He promised, 'He will not do the mistake again.'"

Explanation of the Correct Answer:
· The given sentence is in direct speech, and we need to convert it into indirect speech.
· "Will" changes to "would" in indirect speech.
· "Again" can be replaced with "next time" for better clarity.
· The correct transformation is: "He promised that he would not do the mistake next time."
Other options:
· (b) "would not did" → Incorrect; "did" is the wrong form after "would."
· (c) "will not do" → Incorrect; "will" should change to "would" in indirect speech.
· (d) "promises that he will" → Incorrect; changes the tense, which is not required.
Thus, the correct answer is (a) He promised that he would not do the mistake next time.