If we ____ now to protect the environment, we will live to regret it.
________, I could not memorize the text.
It was the training ________ he had as a young man ________ made him so excellent.
Not until she took off her dark glasses ________ she was a famous film star.
Do not start a book unless you can see from the first few pages that it is ________ you can easily read and understand.
______ is often the case, many Chinese parents save enough money for their children’s further education.