Ian found the camera that Ryan had lost at the beach, so 
OPTIONS:
- Ian felt grateful about being helped out.
- Ryan felt grateful about being helped out.
Ryan felt grateful about being helped out.

Megan was slimmer than Sarah because 
OPTIONS:
- Megan took supplements in order to be healthier and fit.
- Sarah took supplements in order to be healthier and fit.
Megan took supplements in order to be healthier and fit.

The knees of Neil are aching, but Ian's are fine. This is because 
OPTIONS:
- Neil is a young man.
- Ian is a young man.
Ian is a young man.