. He is too tired ________ any longer.
. To our surprise, that top student in our class failed _________a scholarship.
. The building burnt down in a big fire. _________was the base on which it stood.
. If a computer crashes, you will lose the file you _________unless you save it regularly.
. The driver _________, according to the newspaper, to have been killed in the traffic accident.
. The custom of giving gifts at Christmas can be traced back to the Wise Men _________gifts to the baby Jesus.