Problem: How does the sentence end?

Erin was younger than Sarah, so 
OPTIONS:
- Erin had a twitter to communicate with her friends rather than using mailed letters and the phone.
- Sarah had a twitter to communicate with her friends rather than using mailed letters and the phone.
Answer: Erin had a twitter to communicate with her friends rather than using mailed letters and the phone.

Problem: How does the sentence end?

Samuel taught Matthew how to calm his overactive mind because 
OPTIONS:
- Samuel had successfully done so in the past.
- Matthew had successfully done so in the past.
Answer: Samuel had successfully done so in the past.

Problem: How does the sentence end?

I would say Amy is somewhat of a tomboy while Patricia is a girly girl as 
OPTIONS:
- Amy grew up with a brother.
- Patricia grew up with a brother.
Answer: Amy grew up with a brother.

Problem: How does the sentence end?

The towels at my moms house are better than the napkins because the 
OPTIONS:
- towels soak up less water.
- napkins soak up less water.
Answer:
napkins soak up less water.