Why Can Virtual Particles Exist for Only a Very Short

Why can virtual particles exist for only a very short length of time?

A) Virtual particles by their nature have very little energy and thus cannot move very far before they stop.
B) If the particles existed longer than this short length of time, the law of conservation of energy would be violated because real energy would appear from nowhere.
C) If this limited time were exceeded, there would be too many virtual particles in existence at one time, which would violate the Pauli exclusion principle of one particle per set of quantum numbers.
D) Virtual-particle pairs were created only during the era of cosmic inflation and lasted a mere 10-³² s.