Vitamin D helps our bodies make a special chemical, and this special chemical, ________, affects our brains, making us feel happy.
You must have waited here for a long time ,___________you?
Nearly________ of the surface of our planet is covered by water.
It’s said that __________ is going to give us a lecture.
We had ___________ wonderful time_________the party_______ other day.
I don't remember___________ to the airport that year.