Most of the staff is restive under the new manager's rule.

The correct answer is C. uneasy.

The word "restive" means "uneasy or restless, especially because of boredom or confinement." It is often used to describe people who are feeling impatient or frustrated. In the context of the question, it is likely that the staff is feeling uneasy because they are not used to the new manager's style of management. They may be worried about how the new manager will affect their jobs or their work environment.

The other options are incorrect because they do not accurately describe the staff's feelings. Option A, "relaxed," is incorrect because the staff is not feeling relaxed. Option B, "friendly," is incorrect because the staff is not feeling friendly towards the new manager. Option D, "obstinate," is incorrect because the staff is not being stubborn or refusing to cooperate.