The maid was looked after by the child.
The maid was looking after the child.
To convert a sentence from passive voice to active voice, you need to identify the subject, verb, and object in both the passive and active sentences. The structure of a passive voice sentence is generally: Object + Auxiliary verb (be) + Past Participle form of the Main Verb + by + Subject. The structure of an active voice sentence is: Subject + Main Verb + Object.
Thus, the correct active voice form of the given sentence is: The maid looked after the child.