Aword which describes a depressed area of land that has been drained by a river is

The difference(s) between the grand canyon and valles marineris is/are: (a) the grand canyon was formed by water, but valles marineris was not. (a) valles marineris is much longer than the grand canyon. (c) valles marineris is much wider than the grand canyon. (d) valles marineris has large volcanoes near it. all of the above

Which two following best identify the central themes of this speech in the passage the man in the arena

Which type of map gives the most information about what lies below the surface terrain ?