完成对话
A: How was your vacation, Fred?
B: ____ .
A: ____ ?
B: I went to the U.S. with my parents.
A: Cool! ____  in the U.S.?
B: First we went to Los Angeles(洛杉矶). My uncle lives there. Then we went to New York to see my cousin.
A: ____ ?
B: It was a little warm but sunny.
A: Did you see any movie stars in Los Angeles?
B: No, but I saw Tom Cruise in New York. He was at a restaurant! I got his autograph.
A: Wow! That’s great!  What else did you do in New York?
B: Hmm…Oh yeah, I also went to Central Park.____ there! .

795－436得到的差是（____  ），用减法验算应怎样算？（ ____ ）－（ ____ ）=（____  ）。

选择①O₂、②H₂O、③N₂填空（填写序号）

（1）能供给呼吸的气体是　____ 　；

（2）充入食品包装袋中可防腐的单质是　____ 　；

（3）开封的饼干在空气中会回潮变软，是由于空气中含有　____ 　而引起的．