You need a fire to roast marshmallows.

Which of the following is the best way to revise this sentence to include a transition to start the description of a process?

A. Earlier, to roast marshmallows, you need a campfire.
B. To roast marshmallows, afterward you need a campfire.
C. Later, to roast marshmallows, you need a campfire.
D. First, you need a fire to roast marshmallows.