[单选题]
The Michelson-Morley experkpzze/s3. ;yhw d9 oc4i j,sqq6hu1fu; 18rroo ment was designed to measure
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.