Which of following is not an example of mechanical weathering? A a gopher burrowing in the ground and loosening rock/soil. B a tree's roots growing in a cracked rock. C iron oxide weakening and breaking down a rock. D ice expanding cracks in a rock.

On a test the graders have a mean of 77 and a standard deviation of 8. if we can approximate the distribution of these graders by a number distribution what percent of the students. a) scores higher than 77? b) should pass the test (grades > 60)? c) should fail the test (grades < 60)?