In each of the following questions, choose the option that best completes the gap(s). Scarcely ______ she entered the room when the phone rang.

This question tests the use of inversion with negative adverbs. When an adverb with a negative or restrictive meaning (such as scarcely, hardly, no sooner, seldom, rarely) begins a sentence, the subject and auxiliary verb are inverted.

The correlative pattern for scarcely is: Scarcely had + subject + past participle ... when ...

The sentence describes two completed past actions - entering the room and the phone ringing - where one happened immediately before the other. This calls for the past perfect tense (with had) in the scarcely clause, because the past perfect marks the earlier of two past events.

The correct sentence reads: "Scarcely had she entered the room when the phone rang."

The other options fail:

• did would require the base form of the verb ("Scarcely did she enter"), which mismatches the past participle "entered" already present in the sentence.
• has uses the present perfect, but both events are clearly in the past.
• does uses the simple present, which is wrong for narrating completed past events.

Remember: Scarcely...when and Hardly...when always take had + past participle, while No sooner...than follows the same pattern.