--Has he passed the exam yet?  ---No,He ___ it if he had studied harder.

It’s important that the future ______ with a goal of caring for the environment.

—My daughter mastered Japanese in less than two years.—Did she? She         have a gift for language.

He knows it is high time that he ________ at once.

I really don’t know how to express my thanks to Mr. Li, my high school English teacher, without whose help I__________ to college that year.