Crap Shimano gears!!

The wear on the teeth on the 4th gear in the cassette stuck
out pretty obviously, it's definitely hogged out - those teeth do not
look like the teeth in the other gears. The other gears in
the cassette could be fine, I really didn't look that closely.
Sounds to me that she runs in the one gear exclusively. I ride on a
bike path - flat, little altitude change and find that I see wear in
3 of the freewheel rings. Pat