Only when I was told the news ___ that he himself was the great hero.

You don’t know whether the shoes fit you ________ you try them on.

It’s important _______ us students to make a plan _______ our studies before a new term starts.

The doctor said jokingly that his own infection of the virus _______ the discovery of a vaccine (疫苗)of the disease.

_____ the population of the U.S.A. in 2005—It _____ about 296 million.