The Length of the Arrow Representing an Object's Four-Momentum on an Energy-Momentum

Multiple Choice

The length of the arrow representing an object's four-momentum on an energy-momentum diagram is directly proportional to

A) The four-momentum's four-magnitude $|p|$ .
B) The relativistic momentum's magnitude $|\vec{p}|$ .
C) The object's mass.
D) The object's speed.
E) The object's inverse speed.
F) None of the above.