Suppose We Carefully Synchronize Two Identical Atomic Clocks Initially Standing $A$

Multiple Choice

Suppose we carefully synchronize two identical atomic clocks initially standing next to each other (call them $A$ and $B$ ) . We put clock $B$ on a jet plane, which then flies around the world at an essentially constant speed of $300 \mathrm{~m} / \mathrm{s}$ , returning $134,000 \mathrm{~s}(37.1 \mathrm{~h})$ later. We then again compare the two clocks. Assume the earth's surface defines an inertial reference frame, and ignore the possible effects of gravity.
-(a) Which clock measures the space time interval between the synchronization and comparison events?

A) Clock $A$
B) Clock $B$
C) Both
D) Neither