Valles Marineris Is a Wide, Deep Network of Chasms Stretching

Multiple Choice

Valles Marineris is a wide, deep network of chasms stretching for some 2500 miles on the surface of Mars. How do we believe such a big set of canyons formed originally?

A) it was caused by tectonic pressures from deep within the planet
B) it was produced suddenly by flooding water some four billion years ago
C) it was scoured out of the Martian sands by the action of the regular dust storms
D) it was made by hundreds of impacts from space billions of years ago
E) the canyons were places the ancient Martians used for drag racing