In the following statement, one part of the sentence may have an error. Find out which part of the sentence has an error: (A) Shailesh promised / (B) that he would do it / (C) on the next day. / (D) No error

Correct option is C

The phrase "on the next day" is incorrect in this sentence. The correct expression should be "the next day" without the preposition "on" because when referring to time in this specific format, no preposition is needed. “He would do it the next day” is grammatically accurate and commonly used in reported speech.
Explanation of options: (a) A – "Shailesh promised" is grammatically correct. It appropriately sets up the context for reported speech. There is no subject-verb disagreement or tense issue in this part. Hence, it contains no error.
(b) B – "That he would do it" is also correct. It follows proper indirect speech construction after a verb like "promised." It uses the past tense form “would” correctly in a subordinate clause. So this section is error-free.
(c) C – This is where the error lies. The use of "on the next day" is incorrect in reported speech. In indirect narration, the correct phrase is “the next day” without “on.” Including "on" makes the sentence grammatically awkward and incorrect.
(d) D – This option is wrong because the sentence is not error-free. Option C contains a grammatical error, so "No error" is not the right answer in this context.