He was suffering from boredom, the security guard would let him grind his favorite spot on his what?
Options:
- meet interesting people
- listen to music
- deck
- play cards
- skateboard
Let's think now! Step-by-step reasoning:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Grinding is an activity that is performed using a skateboard. Skateboard is a thing. Grinding on a skateboard involves sliding on it.
So, the final answer is skateboard.