Chemical pollution will bring about a threat to agriculture and food chain, and ________ to human health.
--- The floor is dirty. Can anyone clean it?--- ______. I do it all the time.
In the face of ______ failure, it is the most important to keep up _____ good state of mind.
He was always _______ for knowledge, and at last became an expert in the field of art.
______ at the crossing and you will see a tall white building.
Rather than ______ at home playing cards on the Internet, I prefer _______ out for a day trip.