Problem: How does the sentence end?

When Matthew learned how to speed read, Brian criticized him since 
Answer: Brian had a learning disability.

Problem: How does the sentence end?

I couldn't zip the backpack with the book in it because the 
Answer: backpack is too short.

Problem: How does the sentence end?

Christine wanted to go visit the aquarium on the weekend, but not Victoria, because 
Answer: Christine had never been there.

Problem: How does the sentence end?

At the pet store Joel bought a parrot but Brian didn't because 
Answer:
Joel thinks parrots are neat.