A Meson Moving Through a Laboratory of Length X at a Speed

Multiple Choice

A meson moving through a laboratory of length x at a speed v decays after a lifetime T as measured by an observer at rest in the laboratory. If the meson were at rest in the laboratory its lifetime would be:

A) T(1 - v/c)
B) T(1 - v/c) ^-1
C) T(1 - v²/c²) ^-1/2
D) T(1 - v²/c²) ^1/2
E) (T - vx/c²) (1 - v²/c²) ^-1/2