Select the option that expresses the given sentence in passive voice.

The maid was dusting the hall when the door-bell rang.

The door-bell rang when the hall was being dusted by the maid.

The correct option that expresses the given sentence in passive voice is The door-bell rang when the hall was being dusted by the maid.

The other options are incorrect because:

• The door-bell rang by the maid when the hall was dusted is grammatically incorrect. The subject of the sentence is "the door-bell," but the verb "rang" is in the active voice, which means that the subject is doing the action.
• The door-bell rang when the maid was dusting the hall. is in the active voice, not the passive voice.
• The door-bell rang when the maid is dusting the hall. uses the present progressive tense, which is not typically used for actions that happen once.