— You keep on coughing. What’s the matter? —  Oh, I’ve got a cold. Nothing serious, ____.

Nelson Mandela, former president of South Africa, devoted himself        to making the black and white equal.

Although I majored in English, language _______ became a challenge when I set foot in the USA for the first time.

—In early autumn Steve applied for admission to college. He wanted to go      but to Cornell University.—Oh, why not Harvard?

These natural parks are very important for preserving many animals, which would ______ run the risk of becoming extinct(灭绝的)．