_________ many times, but he still couldn’t understand it.
As a global financial center, Hong Kong serves as the ______ role in the course of Renminbi internationalization.
There is a ______ going on in America public schools over the best way to teach English to foreign students.
—Can I go out to play, Mom? —You can ______ you stay in the garden.
All people, ______ they are old or young, rich or poor, have been trying their best to help those in need since the disaster.
______ he works hard,I don't mind when he finishes the experiment.