Hotels fill up fast during the busy tourist season, __________it is necessary for tourists to make reservations in advance.
. This old computer must have been of great use to ____________ did the scientific research.
. .It was _______ he said that _______ me feeling frustrated.
. __________I am amazed at is__________she wants to find fault with others all the time.
. —Is it OK if I have another cup of coffee? —Of course, _______.
. A terrible accident _______,however, occur the other day and we caught sight of it _______ accident.