【单选题】People once widely believed that intelligent life existed on Mars. The 19th-century discovery of what appeared to be geometric designs cut across the surface was taken as evidence. The lines were thou...
A.
Because the surface of Mars seemed to be geometric.
B.
Because the lines were drawn across the surface of the planet.
C.
Because a system of canals was thought to be there.
D.
Because it was the Martians that built the canals.