Which characteristic in soil indicates high humus content

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

What is the reason for the “scramble for africa”?

Lines of longitude are like stripes from the top of the globe down to the bottom virtually slicing the earth like an orange