Which of the Following Statements About Valles Marineris, the Great

Which of the following statements about Valles Marineris, the great "grand canyon system" on Mars is true?

A) it is much shorter than the Grand Canyon in Arizona, but much much wider
B) it was discovered by Giovanni Schiaparelli in the 19th century
C) it was hard to photograph because it is always covered by wind-blown dust
D) landslides have helped broaden the canyons since they were first formed
E) although the canyons are long and wide, they are very shallow, only a few feet deep
Section 10.5: Water and Life on Mars