Select the most appropriate option to fill in blank 1.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. be.
The verb "know" is followed by "to be" when describing a state or identity.
"To be" is the correct infinitive form to describe a fact or characteristic.
Explanation of Incorrect Options:
Been – "To been" is grammatically incorrect.
Had – "To had" is incorrect; "to have been" might work in a different context.
Is – "To is" is incorrect; "is" would be used in a direct sentence, not after "to."
Hence, the chosen option is correct.