Vitamin D helps our bodies make a special chemical, and this special chemical, ________, affects our brains, making us feel happy.
Considering his health, I advise him to ______ an hour or two each day to work out.
Riding bikes has advantages __________ driving cars ________ many aspects.
How can we get this language point _____ to the students.
We' ve published large quantities of books. This year___ we've published three million.
Why not look up the new word in a dictionary _____ you don’t know it ?