How can the requirement to finish an assignment by Friday be phrased using "must"?

The phrasing that uses "must" effectively conveys a strong obligation or requirement to complete the assignment by Friday. When someone says, "You must complete the assignment by Friday," it clearly indicates that this is a non-negotiable requirement, emphasizing the necessity of finishing the task by that deadline.

In contrast, the other options present varying degrees of obligation or advice. For example, suggesting "should" implies a recommendation rather than an obligation, while "could" indicates a possibility rather than a requirement. The phrase "have to" expresses a strong obligation as well, but it typically reflects an external necessity rather than a direct command. Hence, "must" is specific in its intensity and urgency, making it the most appropriate choice for this context.