Now the air in our city is ______ than it used to be. Something must be done to stop it.
Lesson Ten is ____________ in Book Two .
–Look at the clouds , so beautiful ! – Wow , so many different ______ , horses , sheep , flowers…
This is my ___________ second time to come to Beijing .
Japanese can hardly avoid_______ products _____in China.
Only then______ have a chance _____ an astronaut.