Vitamin D helps our bodies make a special chemical,and this special chemical, ____ , affects our brains,making us feel happy.
The weather in the south is generally warm, but it________ be very cold sometimes.
It was the belief _____ Alex Haley could find his “root” in Afric______ made him decide to go to Gambia.
John had made up his mind to give it up, but on _________ second thought he determined to have __________ third try.
— If our team gets the first place, we will get a bonus. With that bonus, I will go for a trip with my girl friend. — _______.
We attend lectures in the school lecture hall at weekend ____ seats more than 800 students.