Final answer:
To change the sentence 'They had fixed the broken window' into passive voice, we need to switch the object 'the broken window' to the subject position, and the subject 'they' to the object position. The passive voice version of the sentence is: 'The broken window was fixed by them.'
Step-by-step explanation:
To change the sentence 'They had fixed the broken window' into passive voice, we need to switch the object 'the broken window' to the subject position, and the subject 'they' to the object position. The verb 'had fixed' remains the same, but we add the auxiliary verb 'was' before it, followed by the past participle 'fixed'. The passive voice version of the sentence is: 'The broken window was fixed by them.'