David apologized for _______ to inform me of the change in the plan.
It is announced that big prizes will go to ________ finishes the assignment on time.
The pupils were playing games in the classroom ________ a gunman entered and began shooting wildly at them.
Actually, the London Olympic Park is built ________ there used to be a poor area called East London.
You had better book rooms at the hotel in advance ________ you should find no room on your arrival.
________ you are unable to deal with it, perhaps we should ask someone else for help.