Multi-choice problem: Continue writing the next sentence in this paragraph:

How to make acidophilus yogurt
Combine 4 cups (950ml) of milk and 3/4 cups (120 g) of powdered milk (if not using whole milk) in the saucepan.
Set the burner to medium heat and place the saucepan on the burner.
Whisk the mixture constantly to keep it from sticking to the pan.

Available options:
A). If the mixture is too liquid, add more milk. Keep whisking and stirring until the mixture reaches a smooth consistency.
B). Do not stop whisking until the mixture thickens and has turned a deep butter gray. Insert a lemon slice into the melted mixture and transfer it to a blending dish.
C). Turn the heat to medium-high and keep whisking. You'll find the mixture thickening and forming a light adhesive on the pan.
D). Gradually heat the milk to 180 to 190 degrees fahrenheit (82 to 87 degrees celsius). Determine the temperature by inserting the instant read thermometer in the milk periodically.
D).