Select the option that expresses the given sentence in Direct to Indirect Speech.
The captain said, "Stand at ease!"

Correct option is D

The correct indirect/ direct speech is (d).
Explain the rules of conversion in detail.
For imperatives, indirect speech uses an appropriate reporting verb ( ordered/commanded/requested/advised) + object + to-infinitive. The comma and quotes are removed; pronouns are adjusted. Here, “Stand at ease!” is a command, so ordered is precise. The implied addressee becomes them.
So: “The captain ordered them to stand at ease.”
· (a) with only said is incomplete/awkward for a command.
· (b) said that… should is possible but less idiomatic than the command structure.
· (c) advised misrepresents the force of a military command.
· Rule recap: Imperative ⇒ Reporting verb (order/ask/request) + object + to + V1; negative imperative ⇒ not to + V1.