Vitamin D helps our bodies make a special chemical, and this special chemical, _______, affects our brains, making us feel happy.
It’s strange that they_____nothing about this matter.
—— Could I use your telephone? —— Yes, of course you _____________.
It’s high time we_______ to the theater.
He______rather stay at home than go to the cinema with you.
I______often go fishing when I lived in the countryside.