Problem: How does the sentence end?

Eric is known as bilingual whereas Jason is not because 
Answer: Jason still can't speak Spanish fluently.

Problem: How does the sentence end?

Steven but not Brett wanted to plant a garden in the backyard because 
Answer: Brett had a black thumb.

Problem: How does the sentence end?

Patricia eventually had to have an artificial hip put in, unlike Rachel, because 
Answer: Rachel had good joints.

Problem: How does the sentence end?

"The ability to finish what you start is what you need to improve", said Michael to Brian,  
Answer:
Michael sometimes has to be the one who takes charge.