This question focuses on converting direct imperative sentences (commands or requests) into indirect speech. When transforming "The officer said, 'Stand up.'" into indirect speech, the structure changes significantly.
For imperative sentences, the reporting verb "said" is typically replaced by a verb that conveys the nature of the command or request, such as "ordered," "commanded," "requested," "advised," or "told." In this context, an officer gives an order, so "ordered" is the most appropriate choice.
The command itself is then expressed using a "to-infinitive" structure. The direct command "Stand up" becomes "to stand up." It's also crucial to include the object of the command, even if it's implied in the direct speech. Since the officer is giving an order to someone, we infer an object like "him" or "them." Therefore, "The officer ordered him to stand up" is the most complete and grammatically correct transformation.
Options A, C, and D are incorrect because they either omit the object of the command, use an incorrect reporting verb, or fail to apply the "to-infinitive" structure properly. The inclusion of "him" clarifies who the order was directed at.