Snowboarding is a sport that began in the United States in the last 40 years, but it did not become an Olympic sport until 1998. In this sport, a rider attaches a snowboard to his feet with a binding similar to skis and then rides down a snowy slope. Some snowboarders ride in a half-pipe, or a large ditch with flat areas at the top. They try to do tricks as they come to the top of the slope on each side. Many snowboarders also ride down a course on a mountain. Many snowboarding competitions let riders show off their skills. Which of the following relationships is most similar to the relationship below?

snowboarding : snow
A.
snowboard : skis
B.
sports : mountain
C.
half-pipe : competition
D.
skateboarding : concrete