Question

the teacher said some students will stay back
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Answer 1

The teacher forbade the student to talk nonsense.

Indirect Speech is used to report something in our own words.

In case of order, the pattern for converting direct speech to reported speech is verb + indirect object + to-clause.

The indirect object is the person spoken to. Verbs in case of order can be command, order, warn, forbid.

Thus, the sentence would be - The teacher forbade the student to talk nonsense.

Hence, option B is the correct answer