The correct answer is B. Before calling Dana, I'll make sure I know what I want to say.
Step-by-step explanation:
Transitions are words included within a sentence or between them to show the relationship between the elements linked, this relationship can be of many types including cause and effect, contrast or chronological order relationship. In the case of chronological relationship this includes words such as before, after, then, next, soon or later that are related to time and therefore express the order events occur.
According to this, the sentence that uses a transition of this type is "Before calling Dana, I'll make sure I know what I want to say" because the word "before" is a transition that indicates chronological relationship; also this has been used correctly because "I'll make sure I know what I want to say" occurs before "calling Dana".