Which sentence is correct in all its punctuation?

a. Although he was busy with other claims, the agent visited the Davises’ home, and arranged for a contractor to remove the tree that day.
b. The situation was quite distressing, but the fast action of the agent and the quick approval of the insurer resulted in a rapid solution.
c. When he heard about the damage; their insurance agent, who lives in nearby Shelby County, immediately called an adjuster.
d. As a result of the hurricane; a ten-ton tree crashed through the Davises’ roof.