--How are your recent trip to Sichuan?—I’ve never had ______ one before. 

 I haven’t seen______ this since I collected stamps.

Water can absorb and give off a lot of heat without big changes in temperature , thus creating a        environment .

Upon reaching an/a ______  age, children are encouraged, but not forced, to “leave the nest”.  

--- What do you think of the good news ? --- Wonderful !．It makes us ____．Most of us were ____about it and _____ looks appeared on their faces．