His father ordered him to go to his room and study.

The correct answer is D. His father said firmly, “Go and study in your room.”

The other options are incorrect because they do not convey the sense of urgency or authority that is present in the original sentence. Option A, “His father said, ‘Go to your room and study,'” is too casual. Option B, “His father said to him, ‘Go and study in your room,'” is too polite. Option C, “His father shouted, ‘Go right now to your study room,'” is too aggressive.

The word “firmly” in option D conveys the sense of urgency and authority that is present in the original sentence. It suggests that the father is serious about his request and that the son should obey immediately.