Identify the part containing a grammatical or structural error:
Hardly had he left the room when the guests have arrived.

Correct option is D

Option (d) contains an error.
Detailed explanation of error: With Hardly/Scarcely … when, the standard sequence is Past Perfect in the first clause and Simple Past in the second. Here we have “Hardly had he left … when the guests have arrived.” The verb phrase “have arrived” (Present Perfect) is wrong after when indicating a definite past point. The correct form is “when the guests arrived.”
Grammatical rule used:
· Structure: Hardly/Scarcely + had + subject + V3 + when + subject + V2.
· Parallel pair: No sooner + had + S + V3 + than + S + V2.
· Inversion occurs after the negative adverb ( Hardly/Scarcely/No sooner).
· Example: Hardly had the bell rung when the students rushed out. / No sooner had I sat down than the phone rang.
· Information booster / exceptions:
· Don’t use Present Perfect with a definite past-time marker like yesterday, last week, when, etc.
· If you notice “quests” in the stem, treat it as a typographical slip for “guests”; the tested error is the tense after when, not spelling.