I have been teaching for over twenty years, but never _____ a girl as bright as Lily.
I recommended strongly that you ______a more powerful computer, even though your brother recommended ______ an ordinary one.
Mr Li began to teach in this school, _______, some time later, she became popular with the teachers and students for her excellent teaching levels.
As the saying goes, practice makes perfect, ______is only by using English as often as possible can you learn English well.
I had no idea how it______ that he should have been late for class three times a week.
The reporters exposed the corruption (腐败) of several high officials in the government; as a result, they ________ to resign from office.