It is written clearly in the requirements that all passengers _______ check onto board thirty minutes before the plane takes off. 

It was playing computer games that cost the boy plenty of time that he ______ spent doing his lessons.

Tom hurried to school only to find that there was none because it was Sunday and he _____to school.

John wants to see me now, but I have so much work on hand that I would  rather he ________ tomorrow than today.

We were stuck at the airport because of the heavy fog, otherwise we ________ here in time for the conference.