Erin kept a close watch on Laura, but 
OPTIONS:
- Erin knew exactly what they were up to.
- Laura knew exactly what they were up to.
Laura knew exactly what they were up to.

Kenneth had a fever, so Kevin gave him some medicine to take. 
OPTIONS:
- Kenneth was his patient.
- Kevin was his patient.
Kenneth was his patient.

The machines were much less effective for slimming the thighs than the weights were, as the 
OPTIONS:
- machines rigorously worked them.
- weights rigorously worked them.
weights rigorously worked them.