Scenario 18-3 Sam Has Two Jobs, One for the Winter and One

Scenario 18-3
Sam has two jobs, one for the winter and one for the summer. In the winter, he works as a lift attendant at a ski resort where he earns $11 per hour. During the summer, he drives a tour bus around the ski resort, earning $13 per hour.
-Refer to Scenario 18-3.If Sam takes fewer hours of leisure in the winter than in the summer,we can assume that his labor supply curve

A) is horizontal.
B) is vertical.
C) is entirely upward sloping.
D) has a backward-sloping portion.