The teacher said to the children, “Do not walk in the sun.”

Indirect : [[1]]

 

 

 

Firstly, According to the meaning of say / said, the Verbs also change their forms; like – ask / asked, beg / begged, tell /told, order/ordered, request / requested, go/went, etc.

Secondly, Inverted commas (“ ”) are removed and instead “not + to + Verb1” is used. 

Example :  ‘do not go’ changes into ‘not to go’, ‘do not make’ into ‘not to make’, ‘do not sing’ into ‘not to sing’, etc.

So, the correct answer is "The teacher asked the children not to walk in the sun".