Answer
The correct answer is:
(a) the time interval measured in a reference frame in which the two events occur at the same place
Work Step by Step
The proper time interval between two events is the time measured in the inertial reference frame in which two events occur at the same point. Note that the proper time interval is the shortest possible time interval for these two events that any observer can measure.
The correct answer is:
(a) the time interval measured in a reference frame in which the two events occur at the same place.
