He is __________ unusual inventor and he invented _________ useful invention.A. a; an B. a; a C. an; an D, an; a
—Do you believe that paper is made ________ wood? —Yes, I do. And you can see that books are made ________ paper.
It seems that something is wrong with Pam. She is always trying to avoid _____my questions.
It was ______ great success that everyone was proud of it.
She used to _______with her parents, but now she is used to ______with her classmates at school.
I was so lucky that I met ______ European man on Three Gorges Square yesterday, and we had ______ happy conversation.