If x-rays are not visible to the human eye, how can we see a doctors x-ray if our bones ?

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

Solve for r in the formula v = ir, when i = 5 and v = 15.

Which describes the solid flying debris from a volcano