By the time he was 38, he had become ________ principal of ________ university.
The boy ________ in the bed ________ to his friend that a cock laid an egg yesterday.
This book ______ 50 maps, _______ 20 of America’s.
Today, we’ll discuss a number of cases______beginners of English fail to use the language properly.
Recently I bought a secondhand car, ______was very low.
—How did you find the talk this morning? —______.