An obtuse angle is defined as an angle that is greater than which of the following?

An obtuse angle is defined as an angle that measures greater than 90 degrees but less than 180 degrees. This definition clearly identifies 90 degrees as the threshold value; thus, any angle exceeding this measurement is classified as obtuse.

In this context, choices like 0 degrees, 60 degrees, and 120 degrees do not accurately represent the definition of an obtuse angle. While an angle greater than 0 or 60 degrees could include a range of angles that encompass acute angles (which are less than 90 degrees), it does not specifically address the requirement for being greater than 90 degrees. Similarly, although 120 degrees is indeed an obtuse angle, it does not serve as the lower limit as required for the question. Therefore, 90 degrees stands as the definitive cut-off point marking the transition from acute to obtuse angles.