Problem: How does the sentence end?

The students took a longer time calculating the physics problem than the engineering problem since the 
OPTIONS:
- physics problem was rather complex.
- engineering problem was rather complex.
Answer: physics problem was rather complex.

Problem: How does the sentence end?

The GM decided to promote Joseph instead of Derrick because 
OPTIONS:
- Joseph is a very capable salesperson.
- Derrick is a very capable salesperson.
Answer: Joseph is a very capable salesperson.

Problem: How does the sentence end?

The payment on the car was less than the payment on the motorbike because the 
OPTIONS:
- motorbike was a nicer vehicle.
- car was a nicer vehicle.
Answer: motorbike was a nicer vehicle.

Problem: How does the sentence end?

Erin was better at driving than Kayla although 
OPTIONS:
- Erin had taken a driver's safety class at school.
- Kayla had taken a driver's safety class at school.
Answer:
Kayla had taken a driver's safety class at school.