The option that uses transitions most effectively is:
"Yeast makes bread rise. There are two types of yeast commonly used in bread making, active dry yeast and instant yeast. Either type can make good bread, but each has been processed differently and thus must be handled differently. Active dry yeast has been heat treated, and as a result the outer layers of cells are dead. Before mixing this kind of yeast with other ingredients, it must first be dissolved in liquid with some added sugar. This step, called proofing, removes the dead cells and activates the yeast. Instant yeast has been more gently dried. Unlike active dry yeast, its outer cells are still alive. Since it does not need to be proofed, it can be mixed directly into other ingredients."
This option effectively uses transitions to clarify the relationships between ideas, emphasizing differences and processes while maintaining a clear flow of information.