You can’t imagine ______ when they received these nice Christmas presents.
I know that it will be difficult to pick him out in such a crowd, but if you ________ happen to see him, give him this packet.
She didn't come to the party last Sunday. ________, she must have made the party more exciting.
Students ________ remain in their seats until all the papers have been collected.
—Did Ann fail in English?—She ________. Don't you notice that she looks depressed?
I wrote a letter to John for his help during my high school years,without which I ________ the college entrance exam.