Fill in the blank with the most appropriate word.
"Don't walk on the bridge." He warned us _________ on that bridge.
The two ways of relating what a person has said are 1)direct and 2)indirect (reported).
In the direct speech, the exact words of the original speaker are repeated.
In the indirect speech (reported speech), the exact meaning of what the speaker told is expressed but not necessarily in the speaker’s exact words.
Option D is correct as the speaker of the direct speech warned them not to walk on that bridge.
Options A, B, and C are wrong as the imperative sentence in the inverted commas is not in the past tense, the given statement is negative, and 'not to' doesn't come in the place of 'don't' respectively.
The correct answer is D)not to walk.