Select the correct option: By the time the adult concludes, the firm_____ its compliance report.

Explanation:

The key phrase here is “By the time”, which indicates a deadline in the future.

👉 Rule:

When one action will be completed before another future action, we use:

• Future Perfect Tense → will have + V3

🧠 Structure:

• By the time + Present Simple
• Main clause → Future Perfect

✔️ In your sentence:

• the audit concludes → Present Simple (future meaning)
• So → will have filed (Future Perfect) ✔️

❌ Why other options are wrong?

• files ❌ → Present Simple (does not show completion before future time)
• will file ❌ → Simple Future (no idea of “completion before”)
• had filed ❌ → Past Perfect (used for past, not future context)

💡 Extra Examples:

• By the time you arrive, I will have finished my work.
• By the time the train reaches, they will have left.

⚡ Quick Tip:

👉 Whenever you see “By the time” (future context)
➡️ Think: Future Perfect (will have + V3)