Water erosion is the main cause which is the loss of topsoil due to water.
All river water comes from melted ice from mountains near them, so the time of year to temp. change depicts how much ice is melted into the river banks.
HNO3 Has a 3 next to the O. this means that there are 3 oxygen atoms.
I would choose D as they both have weather greatly effected by mountain ranges although A my seem like the answer some southern regions of the Midwest are very hot.
CMEs. Coronal mass ejections
