Which is a compound sentence?

Responses
A His mother called to tell him about her impending divorce.His mother called to tell him about her impending divorce.
B When the weather is just right you can see the top of Paris Mountain.When the weather is just right you can see the top of Paris Mountain.
C The printing press broke last night, so everyone's newspaper delivery was delayed.The printing press broke last night, so everyone's newspaper delivery was delayed.
D Although he knew better, John asked her out on a date, and she (surprisingly) said, "Yes!"

C The printing press broke last night, so everyone's newspaper delivery was delayed.