John does important research _______ the best ways to help the old.
Do you know of all the words we used in 2011 "hold" became in China?
—What are you reading these days, Tom?—The book Harry Potter ______ by JK Rowling.
“Tommy, run! Be quick! The house is on fire!” the mother shouted, with clearly in her voice.
Look out! Can you see some boy students ________ basketball?
In a nature reserve , it’s ___ to hunt ______ fish there .