Correct Answer: The contractor instructed the worker to remove all the stains carefully and clean the windows.

Solution : The fourth option is correct.

The given sentence is in the direct speech . As it is a case of instruction, instructed is used in the indirect speech to report.

Narration Conversion:

• Said is changed to instructed , as it is a case of an imperative statement. In imperative sentences, specific words are used to convey the command.
• In the indirect speech, the imperative statement is changed using the infinitive form (to remove) .

Therefore, the correct sentence is: The contractor instructed the worker to remove all the stains carefully and clean the windows.