In the London Olympic Games Badminton Men 's singles final, Lin Dan won the gold medal, becoming the first ____________ the championship.
Neither Tom nor Jack and I ____ his students.
The rich ____ not always happy.
I, who____ your friend, will try my best to help you with your English.
The United States of America _____one of the most developed countries in the world.
The whole class _____the teacher attentively.