Fill in the blank with the appropriate question tag. One can't be too…

The correct answer is Option (1) → can one

Question tags:

• The tag repeats the helping verb of the statement and the same subject as a pronoun.
• A negative statement takes a positive tag (and a positive statement a negative tag).
• When the subject is one, the tag also uses one.
• This sentence: "One can't be too sure" is negative with the helping verb can, so the tag is can one?

Complete sentence: One can't be too sure, can one?

Why the Other Options are Incorrect?

Option 2: might he — Incorrect. Both the helping verb (might for can) and the pronoun (he for one) are changed.

Option 3: can't one — Incorrect. A negative statement cannot take a negative tag.

Option 4: can they — Incorrect. The subject "one" is repeated as one, not "they".