Answer:
D. They worry that Smaug will return while they are visible in the open.
Step-by-step explanation:
J. R. R. Tolkien's fantasy adventure series "The Hobbit" tells the journey of a young hobbit named Bilbo Baggins and some dwarves on their quest for getting the lost kingdom of the Lonely Mountain from the dragon Smaug. The dragon had been sleeping in the palace, not allowing anyone to enter.
The dwarves, with the help of the wizard Gandalf the Grey, had recruited Bilbo to help them out in their quest. Under the leadership of the dwarf King Thorin, they moved towards the Lonely Mountain. The reclaiming of this kingdom meant they had to face the dragon and kill him for the safety of everyone. When they got as bit nearer to the place, they decided to hike to Ravenhill in case the dragon Smaugh detect them coming. They were scared to wake up the sleeping dragon while they are still in the open area.