The tremendous insight of Einstein was that the passage of time does not appear the same while standing still as it does to a person traveling at a substantial portion of the speed of light.
A.
while standing still as it does to a person traveling
B.
to a person standing still as to a person traveling
C.
to a person who is standing still as a person who is traveling
D.
while standing still as to traveling
E.
to a person standing still as to a person who travels