Charles Darwin, a young man just out of university, knew perfect well that he had to depend on _____ when he set out on a voyage of discovery around the world.
He left home in 1980 and has never come back ____.
— Hello, may I have an appointment with the doctor? — ____
— How about a game of chess? — ____
— I’m afraid I can’t finish the book this week. — ____.
— Don’t forget to take the message to my teacher. — ____.