Correct Answer: He told his friend, "You should lose some weight."

Solution : The correct choice is the fourth option.

Direct speech, also known as quoted speech or direct discourse, refers to the representation of someone's words or statements exactly as they were spoken.
The steps of conversion are as follows:

• The reporting verb "suggested" is changed to told.
• There would be no change in the tense because the sentence is an imperative sentence.
• The modal "should" is used after removing the "to + infinitive" from the indirect speech.
• The direct words of the speaker are enclosed in inverted commas.

Therefore, the direct form would be: He told his friend, "You should lose some weight."