Help the spaceship captain finish his official log regarding a disastrous engineering failure. Choose the correct reported modal phrases for each gap.
The chief engineer admitted that he __________________________ a slight miscalculation. He panicked, screaming that the reactor ____________________________ at any minute, and insisted that we ____________________________ the sector immediately.
The correct answers are might have made, could explode, and had to evacuate.
Here is how the engineer's original panicked words shift in the captain's past-tense report:
- "I may have made a miscalculation." (Past possibility). The modal may backshifts to might, keeping the perfect infinitive (have made).
- "The reactor could explode!" (Present/future possibility). The modal could does not backshift; it remains could. Selecting "could have exploded" would incorrectly imply the danger had already passed and the explosion didn't happen.
- "You must evacuate!" (Present/future obligation). When must is used for obligation or commands, it backshifts to had to. "Must have evacuated" would wrongly change the meaning to a past deduction (e.g., "I deduce that you evacuated").