It was really a sinister move on his part.

The correct answer is A. malevolent.

Malevolent means having or showing a desire to harm others. In the context of the question, it is clear that the speaker believes that the person’s actions were motivated by a desire to harm someone.

The other options are not as accurate. Sinful means morally wrong, but it is not clear from the question whether the person’s actions were actually wrong. Auspicious means favorable or promising, but it is clear from the question that the speaker does not believe that the person’s actions were favorable or promising. Right means morally correct, but it is not clear from the question whether the person’s actions were actually correct.