Though ______ to see us，the president gave us a warmwelcome and showed us around

ists are tryingto develop a special material, ________ they will make use of in spacecraft.

May we leave the classroom now — No; you _____. You ______ to leave until the bell rings.

Though Jack was poor and sick, he never ______ any chance to write. That is why he finally became a successful writer.

________ at the cafeteria before, Tina didn’t want to eat there again.