A condition is not optional wording

A fictional paper exercise presents a conditional instruction to line up behind a specifically identified landing aircraft, with the condition repeated at the end. The exercise states that the landing aircraft has not yet passed the relevant point and supplies no further clearance. One learner retains only LINE UP in the readback and proposes immediate entry. Another notices that this removes the condition and treats the words as a take-off clearance. The task asks what the original message establishes and what it does not. No actual runway, traffic separation or aircraft position is supplied beyond the stated classroom assumptions. An answer should retain the condition and distinguish lining up from take-off. It cannot authorize real movement or replace current runway procedures and positive aircraft identification.