Which transformation indicates an obligation to complete an assignment by Friday?

The choice highlighting the strongest sense of obligation is "You must complete the assignment by Friday." The use of "must" conveys a clear directive or requirement, indicating that the completion of the assignment is not just advised but is essential. This phrasing leaves no room for flexibility or personal discretion, representing an obligation that the speaker believes is necessary.

Meanwhile, other options suggest varying degrees of urgency or obligation. The phrase "should" implies a recommendation that is more advisory rather than mandatory, while "will" simply denotes a future action without indicating obligation. The expression "have to" conveys a similar necessity but can sometimes be seen as less formal or authoritative than "must." Therefore, "must" stands out as the clearest choice for indicating a firm obligation.