Modal Verbs of Probability in Technical Communication
5 exercises — must for logical conclusions, may/might for possibility, could for remote possibility, and can't for near impossibility.
0 / 5 completed
1 / 5
The CPU has been at 100% for 20 minutes and no processes are responding. Which modal is most appropriate? "There _____ an infinite loop in the worker thread."
"Must be" expresses a logical deduction from strong evidence. When the evidence is compelling and near-certain, "must" is the correct choice. Compare: "might be" (uncertain), "could be" (possible but not deduced), "can't be" (near impossibility).
2 / 5
A deploy succeeded but some users are reporting 404s. Which sentence best expresses uncertainty? "The routing configuration _____ updated correctly during the release."
"Might not have been" expresses past possibility/uncertainty. "Must not have been" and "can't have been" are both near-certain deductions (negative), which would be too strong when we are simply unsure. "Should not have been" expresses obligation/expectation, not probability.
3 / 5
You see memory usage increasing steadily. Which statement uses the modal correctly?
"Might be" correctly signals an unconfirmed hypothesis during debugging. Using "might" then recommending investigation is a natural and precise debugging communication pattern.
4 / 5
The error log shows a null pointer exception in a function that was refactored an hour ago. "The recent refactor _____ introduced this bug."
"Could have" introduces a past possibility without asserting it as certain. It is appropriate when you have a plausible hypothesis but not conclusive proof. "Must have" would assert near-certainty; "can't have" would deny it.
5 / 5
The feature flag was disabled company-wide. "The new checkout flow _____ the cause — it is disabled for all users."
"Can't be" expresses a logical impossibility based on evidence. Since the feature is disabled, it logically cannot be the cause. This is the negative deduction counterpart to "must be" (positive deduction).