Two Independent Events Occur 100 M Apart with an Intervening $\mu$

Multiple Choice

Two independent events occur 100 m apart with an intervening time interval of 0.42 $\mu$ s.The proper time between the events is:

A) 0 $\mu$ s
B) 0.16 $\mu$ s
C) 0.26 $\mu$ s
D) 0.42 $\mu$ s
E) 0.69 $\mu$ s