The correct answer is A. First, students must fill out their health forms completely. Then, they must head to the gym for orientation.
Explanation:
In writing, sequential organization refers to a pattern of structure of organization in which details in a text are organized in a step-by-step sequence that is usually part of a process, because fo this it is common texts with this organization include transition words that show sequence such as first, second, then, after, later, finally, among others. Considering this, the sentence that uses sequential organization is "First, students must fill out their health forms completely. Then, they must head to the gym for orientation" because this sentence includes details that are part of a process and these are organized sequentially by using words such as "first" and "then" that are commonly used in this pattern of organization.
