[单选题]
The Michelson-Morley expere. fv+v da1; zqt2 /lpxnob/7fiment was designed to meago y:u(gn2) c a)iphe5nyho(.qr /xu8 sure
A. the relativistic mass of the electron.
B. the relativistic energy of the electron.
C. the velocity of the Earth relative to the ether.
D. the acceleration of gravity on the Earth's surface.