Problem: How does the sentence end?

Justin started guitar lessons yesterday, whereas Donald had been playing for ten years, so 
OPTIONS:
- Justin was an expert in their playing.
- Donald was an expert in their playing.
Answer: Donald was an expert in their playing.

Problem: How does the sentence end?

Kayla gave her crush fresh fruit while Lindsey gave her crush a letter because 
OPTIONS:
- Kayla is very romantic.
- Lindsey is very romantic.
Answer: Lindsey is very romantic.

Problem: How does the sentence end?

Amy used her laptop to connect to the Internet instead of her phone, because the 
OPTIONS:
- laptop was so much slower.
- phone was so much slower.
Answer: phone was so much slower.

Problem: How does the sentence end?

Robert likes to do yoga each morning but Jeffrey doesn't because 
OPTIONS:
- Robert has very flexible muscles.
- Jeffrey has very flexible muscles.
Answer:
Robert has very flexible muscles.