Which sentence is the correctly written compound sentence?

AOnce each year, Chincoteague firefighters round up the ponies, set up an auction, and sell some.

BOnce each year, Chincoteague firefighters round up and sell some ponies at auction.

COnce each year, Chincoteague firefighters round up the ponies and sell some at auction.

DOnce each year, Chincoteague firefighters round up the ponies, and some are sold at auction.