Problem: How does the sentence end?

The song took longer to sing than the ballad because the 
Answer: song was more words.

Problem: How does the sentence end?

Kenneth screamed at Benjamin because 
Answer: Kenneth was so upset about the bad experience at the restaurant.

Problem: How does the sentence end?

I couldn't pass my math class even though I hired a private tutor. I guess the 
Answer: tutor was too inept.

Problem: How does the sentence end?

The spots were still visible on the shirt but not on the pants, since the 
Answer:
shirt had been dirtied .