Select the correct indirect form of the given sentence.
She said to Madhu, “Please post this letter.”

Correct option is D

The correct indirect form of the given sentence is (d) She requested Madhu to post that letter.
Direct speech- Direct speech, also known as quoted speech or direct quotation, is a way of reporting someone's exact words.
Indirect speech- Indirect speech, also known as reported speech or indirect quotation, is a way of reporting someone's words or thoughts indirectly, without using their exact words.
Indirect Speech is supported by some verbs like requested, ordered, suggested and advised. Forbid-forbade is used for negative sentences. Therefore,  the imperative mood in the direct speech changes into the Infinitive in indirect speech.
The original sentence is a request, so the indirect form should also reflect a request.