Select the correct indirect form of the given sentence.

‘‘Do your duty’’, the father told his son.

The father advised his son to do his duty.

The correct indirect form of the given sentence is:

The father advised his son to do his duty.

The other options are incorrect for the following reasons:

• The father ordered that his son should be doing duty. - The verb "ordered" is more formal than the verb "advised", and it is also not necessary in this context, as the father is not giving a command.
• The father told to his son to do his duty. - The word "to" is missing before the verb "do".
• The father ordered to his son that to do his duty. - The word "that" is unnecessary in indirect speech.