According to scientists, our mental abilities begin to _____ from the age of 27 after reaching the highest level at 22.
If we expect ____ much cleaner world, we should attract _____ world’s attention to protecting the world.
When water is boiling, steam can be seen ______ from it.
— Would you rather I paid now or later? — As you like, sir. _____.
It’s said that he’s looking for a new job, one ______ he can get more money to support his family.
— Has Tom finished writing his essay today? — I have no idea. He ______ it this morning.