“Where is David?” “He is upstairs ______ ready to go out.”

________ global temperatures rising, the UN Climate Change Conference was held in Cancun（坎昆）, Mexico last year．

How to keep the homeless __________ with food and clothing is still under discussion．

That was such an____question that it made me____,not knowing how to answer.

Rare species in the world, ______ by hundreds every year, must be jointly preserved by all countries, or humans will encounter ecological disaster in the near future.