Can you identify the grammatically incorrect sentence from each set ?

Option 3: "I wish I knew the answer yesterday." is the grammatically incorrect sentence.

The word "yesterday" tells us we're talking about the past. When we use "wish" for past situations, we must use the past perfect tense — "had known," not "knew."

• ❌ I wish I knew the answer yesterday.
• ✅ I wish I had known the answer yesterday.

"Knew" with "wish" only works for present situations, e.g., "I wish I knew the answer right now."

Why the other options are correct:

• Option 1 is a valid mixed conditional — past perfect ("had been") for a past cause, "wouldn't be" for a present result.
• Option 2 correctly uses the past perfect tense to show an action completed before another past point in time.
• Option 4 correctly pairs "as though" with the past perfect ("had happened") to describe something unreal.