Alice Bungee-Jumps from a Bridge Above a Deep Gorge $D$ Be Alice's Departure from Bob's Location on the Bridge, and Watches

Multiple Choice

Alice bungee-jumps from a bridge above a deep gorge. Bob watches from the bridge. Let event $D$ be Alice's departure from Bob's location on the bridge, and event $R$ be her return to Bob's location on the bridge. Carol observes these events from a a train passing over the bridge, and uses synchronized clocks on the train to measure the time between Alice's departure and return.
-(a) Which person's watch or clocks register(s) a proper time between events $D$ and $R$ ?

A) Alice
B) Bob
C) Carol
D) Alice and Bob
E) Bob and Carol
F) Alice and Carol
G) All three observers