By exercise 102, her eyes were burning. Future perfect vs. future continuous. “By this time tomorrow, I ______ (take) the exam.” Will have taken. Correct.

The PDF contained 200 exercises, each one a tiny trap of tenses and prepositions. Lena double-clicked the file. Page one loaded.

She typed the answer in the margin: had known / would have baked . Correct.

Lena laughed. Started. The subjunctive mood. The PDF had taught her that.