Choose the correct sentence from the options below:

Concept: Two related passive-voice rules apply here. For an imperative (command) sentence, the active pattern 'Verb + Object' becomes 'Let + Object + be + Past Participle' in the passive — for example, 'Open the door' becomes 'Let the door be opened.' For an interrogative sentence whose wh-word is the object of the preposition 'by', that pronoun must be 'whom' (not 'who'), and the auxiliary verb is placed immediately after 'by whom' — for example, 'Who broke the window?' becomes 'By whom was the window broken?'

Application: Applying the imperative rule to the active sentence 'Give the order': the object 'the order' follows 'Let', and the verb becomes 'be given', producing 'Let the order be given.' Applying the interrogative rule to 'Who broke the window?' would give 'By whom was the window broken?' — the option 'By who the window was broken?' instead keeps 'who' and does not invert 'was' ahead of 'the window', so it does not follow this pattern.

Cross-check: Reversing 'Let the order be given' to the active voice gives 'Give the order', a complete, standard imperative sentence, which confirms the transformation is grammatically sound. Read purely as a grammar check, more than one of the four options is a well-formed English sentence: 'English is taught to us by Hariharan.' and 'I was shocked by his conduct.' are also grammatically correct. This item is best treated as a passive-voice transformation exercise; Tripura Public Service Commission's final answer key for this Preliminary Examination (recruitment to Miscellaneous Posts, held 20 December 2015) resolves it, recording 'Let the order be given' as the keyed answer to this question.

Contrast with the other options:

• 'By who the window was broken?' — uses 'who' as the object of 'by' and does not invert the auxiliary 'was' ahead of the subject, so it is not correctly formed as a passive question.

• 'English is taught to us by Hariharan.' — a grammatically valid, well-formed sentence; it is not, however, the option the TPSC official answer key selects for this question.

• 'I was shocked by his conduct.' — a grammatically valid, well-formed sentence; it is not, however, the option the TPSC official answer key selects for this question.