Problem: How does the sentence end?

Rewards could encourage the child to behave, while punishments made her worse, since the 
Answer: rewards were so effective.

Problem: How does the sentence end?

Neil is very creative, Kyle is not therefore 
Answer: Kyle does not want to be a graphic designer.

Problem: How does the sentence end?

The teacher said that Brett was unable to learn the language like Joel, by reason that 
Answer: Joel always studied.

Problem: How does the sentence end?

Eric wore a cape and held Samuel and flew them to safety from the villains. 
Answer:
Samuel is a normal mortal.