Volunteering is becoming more and more popular in the world because it gives us a/an __________ to value (珍惜) what you have, and focus on the truly important things in our life.
_____ the students in our school is about 5000,_______ of them are boys.
________ plastic bags we use, ________ it will be to the environment.
Noise pollution can cause people to become sick. So our government has done________to stop it.
He _______ his head to see the _______ sun.
-These farmers have been to the United States. -Really? When _______ there?