B. Eager to eat, Caleb immediately joined the buffet line.
The other ones don't make sense because the order that the words are put confuses who is doing the action.
For example in the sentence:
Caleb was ready for the party wearing a suit and tie.
The way this sentence was written makes it seem like the party was wearing a suit and tie even though it was Caleb.
This is how it should have been:
Caleb, wearing a suit and tie, was ready for the party
Another example:
Having fun, the dance floor was already full of people.
Who/what was having fun? The dance floor or the people? In this sentence it seems like the dance floor is having fun.
This is how it should have been:
The dace floor was already full of people having fun.
Last example:
He rode in a car that was decorated with his friends
So his car was decorated with little models of his friends. I'm sure he didn't mean this so...
With his friends, he rode in a decorated car.
Hope this made sense and helped you understand!