Can you identify the grammatically incorrect sentence from each set?

Option 1 → "The movie starts at 7 pm, so we leave at 6." — The first part is fine because scheduled events (like movie timings) can use simple present tense. However, the second part ("we leave at 6") is a personal decision about the future, not a fixed schedule. It needs a helping word like should, will, or need to. A correct version: "The movie starts at 7 pm, so we should leave at 6." ❌

Option 2 → "She had been working on the report all night." — Correctly uses the past perfect continuous tense (had been + working) to show an action ongoing before another point in the past. ✅

Option 3 → "No sooner had he opened the door than it slammed shut." — Correctly uses the "No sooner… than…" structure with inverted word order (had he instead of he had) to describe two events happening one right after the other. ✅

Option 4 → "By next month, they'll have been married for 25 years." — Correctly uses the future perfect tense (will have been) to describe something that will be completed by a specific future time. ✅

Hence, Option 1 is the grammatically incorrect sentence because the second part expresses a personal future plan, not a fixed schedule, and needs a modal verb like should or will.