It is equally well known that a GPS satellite needs an extremely accurate clock to function correctly; it is less well known however, that GPS satellites also need to adjust for the effects of time dilation, because time passes more slowly on the satellite than it does on earth.(A) It is equally well known that a GPS satellite needs an extremely accurate clock to function correctly; it is less well known however, that GPS satellites also need to adjust for the effects of time dilation, because time passes more slowly on the satellite than it does on earth.
(B) An extremely accurate clock is as essential to the functioning of a GPS satellite as is the need to take a phenomenon, called time dilation, according to which time passes relatively slowly on the satellite than on the earth, into account.
(C) An extremely accurate clock is as important to the correct functioning of GPS satellite as to taking into account a phenomenon called time dilation because time passes slower on the satellite than that on the earth.
(D) Because time passes slowly on the satellite than on earth, due to time dilation, an extremely accurate clock is needed for the proper functioning of a GPS satellite so as to account for the same.
(E) From the perspective of an observer on the earth, time passes more slowly on the satellite than on the earth; this phenomenon, called time dilation, must be taken into account for even a GPS satellite equipped with an extremely accurate on-board clock to function correctly.
Source : Jamboree