Answer: Since there is no article for this then I'm guessing B because it is more logical than the other options.
Explanation:
The answer to you're question is D
A blimp needs to be moored when not flying because plenty of space is needed so the blimp has to be free. They have to be moored by the front end to a tall mast on a truck specially equipped for this purpose.
I have Aviation History so I kinda of undertsnd.
HOPE THIS HELPS. :)
