Fill in the blank with a suitable preposition.
The crew was _______ schedule because of the delay at the airport.
The preposition ‘behind’ means to be late or lagging behind in something. In the given sentence the crew is falling back on their schedule because of the delay in the airport. Therefore option D is correct. Whereas the preposition ‘for’ generally refers to a period of time or is used to denote a reason. The crew is not supporting the schedule because of the delay at the airport, therefore, option A is incorrect. ‘At’ is used to speak about a specific time, which is unsuitable here. Therefore option B is incorrect. The preposition ‘before’ is used to refer to an action that precedes another action or to mean being early. Since the sentence focuses on the delay ‘before’ is unsuitable. Hence option C is incorrect.