A man rides his dirt bike on a track by the airport.
This justifies what answer for what question? Q & A: 
If "Dirt biker on a professional riding course near an airport." does that mean that "Composed of dirt."?
Options:
- yes
- it is not possible to tell
- no
it is not possible to tell
A man rides his dirt bike on a track by the airport.
This justifies what answer for what question? Q & A: 
user
If "Dirt biker on a professional riding course near an airport." does that mean that "Composed of dirt."?
Options:
- yes
- it is not possible to tell
- no
it is not possible to tell
assistant
A man rides his dirt bike on a track by the airport.
This justifies what answer for what question? Q & A: 
If "Dirt biker on a professional riding course near an airport." does that mean that "Composed of dirt."?
Options:
- yes
- it is not possible to tell
- no
it is not possible to tell