Problem: How does the sentence end?

My sister's suitcase was more massive than my bag, because the 
Answer: bag held less stuff.

Problem: How does the sentence end?

Matthew had cleaner hair than Adam did because 
Answer: Matthew washed their hair almost every day.

Problem: How does the sentence end?

The factory worker had a hard time loading the furniture on the truck because the 
Answer: furniture was too big.

Problem: How does the sentence end?

The fisherman couldn't attach the motor to the plank on his boat, because the 
Answer:
motor was too heavy.